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Ministry of Energy Mines and Responsible for Core Review

R - Industrial Rocks

(Example Deposits)

BC Profile # Deposit Type Approximate Synonyms USGS Model #
R01 Cement shale - - - -
R02 Expanding shale - - - -
R03 Dimension stone - granite - - - -
R04 Dimension stone - marble - - - -
R05 (covered in R03) Dimension stone - andesite   - -
R06 Dimension stone - sandstone - - 30d*
R07 Silica-rich rocks High-silica quartzite 30e*
R08 Flagstone - - - -
R09 Limestone - - - -
R10 Dolomite - - - -
R11 Volcanic ash - pumice - - - -
R12 Volcanic glass - perlite - - IM25ka*
R13 Nepheline syenite - - - -
R14 Alaskite - - - -
 R15* Crushed rock Road metal, Riprap, Railroad ballast - -

 

Cement "Shale"

R01
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Claystone, mudstone.

 

COMMODITIES: Cement shale.
 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  Dunsmuir shale -  Nanaimo area (Haslam shale; 092F 345), Sumas Mountain (Huntingdon Formation), Buse Lake, Wabamum shale and Wapiabi shale in Alberta.   

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  Sedimentary rocks with a high clay mineral content such as claystone, mudstone and shale. Rock must provide silica and alumina and contain very small amounts of sodium, potassium and magnesium minerals to be used for cement manufacturing. The presence of sulphur in any form is considered detrimental.

 

TECTONIC SETTINGS: A variety of sedimentary basins: foreland, forearc or island arc type; also oceanic environments. In a continental setting: rift- and graben-type basins, lacustrine depressions and continental shelves.

Sedimentary rocks with a high clay mineral content such as claystone, mudstone and shale. Rock must provide silica and alumina and contain very small amounts of sodium, potassium and magnesium minerals to be used for cement manufacturing. The presence of sulphur in any form is considered detrimental.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTINGNonmarine and shallow marine basins with low-energy environments. Oxidizing sedimentary environments.


AGE OF MINERALIZATIONPaleozoic to Tertiary. In British Columbia, the best deposits occur in Tertiary lacustrine sedimentary basins.


HOST/ASSOCIATED ROCK TYPESCement “shales” have a broad compositional range in clay and silt content, from argillite to siltstone. The host sequence typically includes sandstone, conglomerate and sometimes coal seams or tuffaceous sediments.


DEPOSIT FORMStratiform, bedded sediments. May be flat or deformed by folding and faulting. Lacustrine deposits are from several to tens of metres thick with a lateral extent of several hundreds of metres to a few kilometres. Marine deposits are much more extensive.

 

TEXTURE/STRUCTURELaminated, frequently with thin silty or sandy interbeds in lacustrine deposits. Marine shale is more uniform in composition.


ORE MINERALOGY [Principal and subordinate]: Pyrite; gypsum, chlorides, sulphates and Mn minerals.


GANGUE MINERALOGY [Principal and subordinate]: Waste consists of altered, fractured and unsound rock; stone containing inhomogenities, like blacks knots and aggregates of mafic minerals; and any minerals that  upon weathering could produce stains, e.g. pyrite, chalcopyrite.

METAMORPHIC MINERALOGYMetamorphism can lead to increased sodium and potassium content and recrystallization into harder rocks with a higher melting point.


WEATHERINGAlteration of pyrite improves the acceptability of the weathered shale for the cement industry. A similar effect has a possible decrease in alkali content due to converting illite into kaolinite and the chemical weathering of feldspar in original sediment. Also soluble salts – chlorides and sulphates – can be removed during the weathering process.


ORE CONTROLSNo specific ore controls for shale used to make cement. A wide variety of shale can be used.


GENETIC MODELSClay-rich sediments are generally a product of the chemical weathering of aluminosilicate minerals. These can be accumulated in lacustrine as well as in marine environments. Kaolin is the preferred weathering product.

 
ASSOCIATED DEPOSIT TYPESCeramic clays (E07), expanding clays (R02) and coal seams (A02, A03, A04, A05).


COMMENTSIn some instances, where a clay resource is not available locally, industry is using anorthosite instead.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATUREHigh alumina and silica, very low sodium, potassium and magnesium. Some iron is acceptable.


GEOPHYSICAL SIGNATUREGeophysical methods are not used.


OTHER EXPLORATION GUIDES:  The most readily ascertainable regional attribute is lacustrine sediments associated with coal seams. Marine shale with a thick weathered profile, or deposited in a nonreducing environment.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  The main components in cement clinker are 62.5–63.5% CaO, 21–22% SiO2, 4–6% Al2O3 and 2–3% Fe2O3. Presence of deleterious minerals containing Na, K and S must be carefully

monitored. Depending on the purity of limestone, some of the latter three elements may be part of the carbonate rock. Cement “shale” can add the necessary silica and alumina to obtain roughly the required chemistry for the clinker. Any deficiencies in silica or iron contents can be corrected by adding quartz or iron oxide; in some instances even bauxite may be added to increase the alumina content. Therefore, the industry often uses the nearest acceptable “shale” and adjusts by adding other feedstock. The noncarbonate component in cement mixture is only 22%. Typical cements contain between 0.5% and 1.5% of combined Na2O and K2O. Sometimes only a weathered zone of shale deposit can be used.


ECONOMIC LIMITATIONSThe current standard for making Canadian cement is between 0.6% and 1.0% combined Na2O + K2O in the final clinker, which usually comes from the shale. As well, the shale should be

 

homogeneous and not very difficult to grind. As a low-value commodity, cement shale is generally restricted to local markets. Cement and clinker, on the contrary, are higher-value commodities; therefore, they can travel longer distances.


END USESAs a source of silica and alumina (and sometimes iron) in cement manufacturing.


IMPORTANCE:  A typical North American cement plant has a capacity of 1 million tonnes of cement annually. Consumption of cement “shale” is tied closely to the capacity of local Portland cement plants and the demand for cement and cement products in general. Deposits are relatively common throughout the continent and the world; however, they may be scarce locally. Shale makes up approximately 30% of Portland cement.

 

 

REFERENCES

 

Ames, J.A., Cutcliffe, W.E. and Macfadyen, J.D. (1994): Cement and cement raw materials; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 295–316.

Harben. P.W. (1995): The Industrial Minerals HandyBook; Metal Bulletin PLC, London, UK, 253 pages.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals—A Global Geology; Metal Bulletin PLC, London, UK, 462 pages.

Kuzvart, M. (1984): Industrial Minerals and Rocks; Elsevier, New York, 454 pages.

McCammon, J.W. and Robinson, J.W. (1970): Dunsmuir Shale Pit; in Geology, Exploration and Mining in British Columbia, BC Ministry of Energy, Mines and Petroleum Resources, page 496.

Murray, H.H. (1994): Common clay; in Carr, D.D., Senior Editor, Industrial Minerals

and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 247-­248.

Read, P.B. (1996): Industrial mineral potential of the Tertiary rocks, Vernon and adjacent map areas; in Geological Fieldwork 1995, BC Ministry of Energy, Mines and Petroleum Resources, Paper 1996-1, pages 207–218.

Rodgers, M.C. (1995): Clay and Shale; in Rogers, M.C., Thurston, P.C., Fyon, J.A., Kelly, R.I. and Breaks. F.W., Editors, Descriptive Mineral Deposit Models of Metallic and Industrial Deposit Types and Related Mineral Potential Assessment Criteria; Ontario Geological Survey, Open File Report 5916, pages 168–171.

Stonehouse, D.H. (1984): Cement in Canada; in Guillet, G.R. and Martin, W., Editors, The Geology of Industrial Minerals in Canada, The Canadian Institute of Mining and Metallurgy, Special Volume 29, pages 307–310.

Virta, R.L. (2001): Clay and shale; in Mineral Industry Surveys, United States Geological Survey, pages 18.1–18.27.

 

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Expanding Shale

R02
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Bloating shale, coated lightweight aggregate, pyroplastic clay/shale/slate and a number of commercial product names.

 

COMMODITIES (BYPRODUCTS): Lightweight aggregate (pozzolan).  Explanding slate may be a by-product of roofing slate.
 

EXAMPLES (British Columbia (MINFILE #) - Canada/International)Saturna Island (092B043), Regal (092B085), Niagara Creek (092B046); Upper Cretaceous Wabamum shales in Alberta, glaciolacustrine clays in Alberta and Saskatchewan.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONBeds of claystone and mudstone or "shale" and slate, deposited usually in low energy marine or lacustrine environments. The rock expands to produce a porous, volcanic cinder or slag-like material when rapidly heated to 1000 to 1300 °C.

 

TECTONIC SETTINGS: Wide variety of sedimentary basins, including oceanic foreland, forearc or island arc type, and also rift and graben type basins, lacustrine depressions and shelf accumulations in the continental environment.  

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: In British Columbia form in primarily low energy environments in Upper Cretaceous and Tertiary non-marine and shallow marine sedimentary basins. Elsewhere also form in deep sea shales, lacustrine basins, glaciolacustrine lakes and turbidites.  Low energy, subaqueous anaerobic depositional environments collecting primarily mud over long periods of time. Deposits can be distal from erosional source or associated with source producing only fine clastic material.


AGE OF MINERALIZATIONPrecambrian to Holocene.


HOST/ASSOCIATED ROCK TYPES: Host rocks are argillite, mudstone, siltstone, shale and slate occurring within sequences of sandstones and conglomerates, with or without coal, and a very minor carbonate component.


DEPOSIT FORMStratiform, bedded deposits, may be flat or deformed by folding and faulting. The deposit thickness may be from several tens to hundreds of metres, lateral extent of kilometers or more within beds that can be much more extensive.

 

TEXTURE/STRUCTUREExpanding shale, slate and clay are usually thinly to thickly laminated, fairly uniform in appearance along strike. Some lacustrine deposits may be thickly bedded to almost massive. Depending on level of lithification, some may exhibit a conchoidal to semi-conchoidal fracture.


ORE MINERALOGY [Principal and subordinate]Clay minerals (illite, smectite, kaolinite), silica, feldspar, mica, calcite.


GANGUE MINERALOGY [Principal and subordinate]Interbeds of siliceous siltstone and sandstone; pyrite, gypsum and amorphous carbon.


WEATHERINGAlteration of illite and smectite clays into kaolinite, oxidation of pyrite and/or leaching away of carbon may result in loss of expanding properties.


ORE CONTROLSThe introduction of volatile component (molecular water like in finely dispersed gypsum, some clay minerals or some organic substances) and a fluxing component (alkalies such as feldspar) that melts the rock at the same temperature at which the volatile component escapes.

 
GENETIC MODELSClays and silts are deposited in a reducing environment with very small amounts of other materials. Gas is trapped in the sediment and incorporated into a "shale' during lithification. Marine, littoral, lacustrine and fluviatile clays, shales and slates are all possible expanding products. Low grade metamorphism (for example shale to slate) may not hinder the expanding properties.

 
ASSOCIATED DEPOSIT TYPESCommon clays and shales (E07), cement shales (R01), coal seams (A02, A03, A04, A05), black roofing slate.

 


COMMENTS:  A variety of admixtures (for example carbonate, sulphate and organic-added in minor quantities to common, non-bloating clays can produce expanding properties. This process has been  used commercially on a minor scale where natural expanding materials are not available. In recent years, the US EPA has been developing a process to use the municipal wastes as admixture in clays to produce the lightweight aggregate.


EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE:   Favourable shales usually have between 52 – 80 % SiO2, 11 – 25 % Al2O3 and 10-25% combined fluxes (Fe2O3,FeO, S, CaO, MgO, P2O5, Na2O, K2O, NO3).

 

GEOPHYSICAL SIGNATUREGeophysical methods are not utilized.


OTHER EXPLORATION GUIDES:  Most readily ascertainable regional attribute is the depositional environment with a thick shale or argillite sequence. Economic deposits occur within homogeneous, argillitic sediment sequences, deposited usually in a reducing environment.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  Certain clays, shales and slates have the property of expanding into a porous product when heated rapidly to 1,000 to 1,300 degrees C. The fusion into a viscous form and evolution of the gas must take place simultaneously. This gas may be oxygen, sulphur dioxide, or carbon dioxide. Illitic and montmorillonitic sediments are more favorable for expansion, as are  darker colored and unweathered shales. Thinly fissile slates tend to expand unidimensionally, which is undesirable. Depending on its end use, expanded shale product must meet a variety of quality specifications. Unit weight of expanded product may vary from 881 to 1121 kg/m3. Depending on the final concrete product, there are requirements for compressive strength, ignition

 

loss, adsorption and sizing. Material should be homogeneous and free of hard interbeds, such as quartzite. Distribution of the volatile component may have impact on product density and its homogeneity.can influence quality. Homogeneity is an important quality parameter. The reported average annual production capacity for operating plants in the United States in 1970 was 150,000 tons per year. The present U.S. total annual production is 3.8 million tones from plants operating in 16 states. In Canada, three producers report annual sales of  between 200,000 and 400,000 m3.

 

 
ECONOMIC LIMITATIONS: Expanded shales are often developed primarily as a lightweight aggregate in regions lacking sources of quality hard rock aggregate and sand and gravel and distant from sources of pumice and volcanic cinder. Therefore, the relationship between production expenses and transportation cost is very important in competition with alternative materials. The consumption of lightweight aggregates declined during the late 1970's and 1980's due to rising energy costs and the use of high performance concrete. During the last decade, the production levels in North America kept steady.

 

END USES:  Specialty aggregate for insulation, particularly for water and sewer systems on the prairies (about 50%), and low density concrete products.  Small quantities are also used in horticulture. 

 

IMPORTANCERelatively common deposits throughout North America and the world.  Particularly important for durable, inorganic insulation around water lines and other thermally sensitive infrastructure in cold regions with deep freezing of surface in winter time, also in areas lacking standard construction aggregate sources. There is research into recycling fly ash and other waste products as an alternative for expanding shale.

 

 

REFERENCES

  

Bush, A.L. (1973): Lightweight Aggregate; in Brobst, D.A. and Pratt, W.P., Editors, United States Mineral Resources, U.S. Geological Survey, Professional Paper 820, pages 233-355.

Conley, J.E., Wilson, H., Klinefelter, T.A. and others (1948): Production of Lightweight Concrete Aggregates from Clays, Shales, Slates, and Other Materials; U.S.Bureau of Mines, R.I. 4401, 121 pages.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals – A Global Geology; Metal Bulletin PLC, London, UK,462 pages.

Kuzvart, M. (1984): Industrial Minerals and Rocks, Elsevier, New York, 454 pages.

Mason, B.H. (1994): Lightweight Aggregates; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 343-350.

McCammon, J.W. (1966): British Columbia Lightweight Aggregates Ltd., in Minister of Mines and Petroleum Resources Annual Report, Province of British Columbia, page 264.

McCarl, H.N. (1975): Aggregates-Lightweight Aggregates; in Lefond, S.J., Industrial Minerals and Rocks, American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., New York, pages 85-96.

Vagt, O. (2002): Mineral Aggregates; in Canadian Mineral Yearbook 2000, Minerals and Metals Sector, Natural Resources Canada, pages 34.1-34.8

Virta, R.L. (2001): Clay and Shale; in Mineral Industry Surveys, U.S. Geological Survey, pages 18.1-18.27        

 

 

 

Dimension Stone - "Granite"

R03
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

Hora, Z.D. (2007): Dimension Stone "Granite", in Selected British Columbia Mineral Deposit Profiles.

 

IDENTIFICATION

 

SYNONYMS: Commercial term "granite" for dimension stone includes all fine, medium and coarse-grained, igneous rocks and some metamorphic rocks.

 

COMMODITIES (BYPRODUCTS): Dimension stone blocks and a variety of shaped, split products (aggregate, rip-rap).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International): Kelly Island (092F 196), Fox Island (092F 378) Nelson Island (092F 189), Squamish (092GNW067), Ashlu River (092GNW070), Elaho River (092JW041), Skagit Valley (092HSW159), East Anderson River (092HNW075), Beaverdell (082ESW169), Okanagan Sunset (082LSW068), Pacific Pearl (082ENW083), Nelson (082FSW343); Sudbury, Vermilion Bay (Ontario), Lac Saint-Jean, Saint Didace, Riviere a Pierre (Quebec), Black Hills (South Dakota), Massachusets, Georgia, Vermont, North Carolina; Sardinia (Italy), Norway, Finland, India, Brazil.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  Dimension stone deposits in plutonic intrusions of granite, syenite, gabbro, anorthosite and other igneous rocks.  Fresh, unaltered rock masses with jointing at least 2 metres apart and an absence of microfractures may be suitable for quarrying.  Quarriable bodies may be up to several hundred metres large, but are not very common since the majority of intrusives have high frequency of joints. 

 

TECTONIC SETTINGS: Granitic plutons in subduction setting, zones of extension, back-arc spreading, island-arc environment. In continental setting, alkaline intrusions associated with extensional tectonic and rift zones.

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Synorogenic and post-orogenic intrusions emplaced at different levels within the earth crust. Post-orogenic intrusions are considered more apt to be free of internal strain and to make a better quality dimension stone.

AGE OF MINERALIZATION: Precambrian to Tertiary.

HOST/ASSOCIATED ROCK TYPES: The host intrusive rocks are a variety of compositions, including granite, syenite, diorite, gabbro and anorthosite. Higher grade metamorphic equivalents are also produced under the “granite” name. Associated rocks can be related dikes and pegmatites.

DEPOSIT FORM: Massive unfractured parts of large intrusive bodies without exfoliation features and particularly lacking systems of microfractures. Usually a sound core or large mass, several hundred metres to more than one thousand metres in diameter, irregular in shape, that is surrounded by more fractured and microfractured rock. The size of some bodies may increase with depth; however, even deeply eroded intrusives can exhibit microfractured areas. A single intrusive body may contain several such bodies separated from each other by fractured rock. In more deeply eroded areas, large groups of exfoliated huge boulders may provide a source of commercial blocks.

 

TEXTURE/STRUCTURE: Texture is typically granular, but may be gneissic, either homogeneous or banded, with parallel alignment of mineral grains. Commercial stones are coarse to fine-grained, sometimes porphyritic with feldspar phenocrysts in intrusive rocks, or augen aggregates in metamorphic ones. Augen gneiss can be an attractive commercial stone. Good quality dimension stone has a well developed interlocking texture.

ORE MINERALOGY [Principal and  subordinate]: Most commonly an interlocking texture composed of feldspar, quartz, hornblende, pyroxene and mica. Some commercial stone is composed of a single mineral, such as pyroxenite or anorthosite. Coarser grained mica may be detrimental for the stone to take a good polish.

GANGUE MINERALOGY [Principal and subordinate]: Waste consists of altered, fractured and unsound rock; stone containing inhomogenities, like blacks knots and aggregates of mafic minerals; and any minerals that  upon weathering could produce stains, e.g. pyrite, chalcopyrite.

ALTERATION MINERALOGY: Typically rock must be fresh to be useable. But some alteration products, epidote for example, can produce attractive colour or veining without affecting the physical properties of the stone.

WEATHERING: Chemical weathering may affect the stone by producing unsightly stains as a result of leaching soluble components, particularly iron, and occasionally also copper. Undesireable minor components, like pyrite or other sulphides, and some other iron and manganese minerals, in dimension stone may oxidize and stain in contact with moisture. This may differ in distinct climatic zones; stone with excellent performance record in continental climate may be very sensitive to a coastal climate (salt), or smog-filled air in large cities. Also, not all biotite, or even pyrite, may be sensitive to weathering. Some feldspars and altered feldspars, olivine, hornblende and pyroxene are more sensitive to the loss of polish then other minerals. Physical weathering produces structural deterioration and decreases strength and durability. This is particularly important for stones affected by development of microfractures, especially in climatic areas with frequent freeze/thaw cycles which can cause flaking.

ORE CONTROLS: Frequency of joints and any change in composition, colour, or texture which affects significantly the look and performance of the stone.

GENETIC MODEL: Due to the cooling of magma and tectonic processes, intrusive rocks develop joints and fractures of variable frequency. Also, the presence of volatile components and hydrothermal processes may affect the soundness of the rocks.

ASSOCIATED DEPOSIT TYPES: Marble (R04), andesite (R05), and sandstone (R06) dimension stone, Alaskite (R14) and anorthosite (as a cement raw material).

COMMENTS: Requirements for soundness, homogeneous character and absence of components producing staining generally excludes granitic rocks in areas of metallic mineralization.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: NIL

GEOPHYSICAL SIGNATURE: Resistivity surveys have been used to identify low fracture densities and deeply weathered zones in areas with Pleistocene cover. Also, well developed microfracturing in contrast with the sound stone can be outlined by a resistivity survey. Some intrusions will have strong, positive or negative, magnetic or gravity signatures that could be used to identify their location or extent.

OTHER EXPLORATION GUIDES: Intrusive rocks showing consistent and uniform colour with few fractures or forming large boulders. Prospect for large boulder fields as a result of exfoliation and unfractured and smooth rock faces exposed along mountain slopes. Use air photo studies to locate probable areas of intrusions with few large fractures. The type of physical weathering can distinguish an unsound stone, particularly a sharp, angular and raspy surface and angular, detrital feldspar are indicators of low strength and high absorption of water.
 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Opening face should be at least 50 metres long; some quarries can reach a thousand metres wide. Physical properties of stone are an important aspect and have to meet American Society for Testing and Materials Standards (ASTM). These may significantly differ depending on the end use. Outside wall cladding is much more demanding on the strength than for example a floor tile. As BC producers have proven, even a small operation of few thousand tonnes per year from a quarry site can be a successful business venture.

ECONOMIC LIMITATIONS: Waste to commercial size block is an important economic factor. This changes within the deposit as well as from deposit to deposit. If the quarry can sell the waste for aggregate or other commercial products, like split facing stone, landscaping chips and roofing chips, then a more fractured common granite can afford larger waste to block ratio. As a rule of thumb, common types of granite can afford some 20% of waste, while the high end value stone (Blue Pearl larvikite) can have waste up to 80% of quarried rock. For exterior applications, the stone should take good, uniform and lasting polish with good frost resistance. Transportation is a major cost of the finished product. Common types of granite can compete in local markets only, while special varieties (black, red, blue) can travel worldwide.

END USES: Granite tile, facing sheets, monumental stone, and masonry blocks. Waste rock can be used for ashlar, curbing stone, flagstone and facing chips, paving stone and aggregate.

IMPORTANCE: This deposit type is a main source of granite for dimension stone applications.
 

REFERENCES

 

Anonymous (1995): Stone Report: Canada, Dimensional Stone, Volume 11, Number 10, pages 36-62.
Alseth, J. (1995): Current Thoughts on Stone Testing, Dimensional Stone, Volume 11, Number 10, pages 25-35.
Barton, W.R. (1968): Dimension Stone, U.S. Bureau of Mines, IC 8391, 147 pages.
Bates, R.L. and Jackson, J.A. (1987): Glossary of Geology, American Geological Institute, 788 pages.
Bellemare, Y. (2002): Exploitation de la Pierre de Taille au Quebec Dans la Province de Grenville de 1983 a 1997; in Dunlop, S. and Simandl, G.J., Editors, Industrial Minerals in Canada, Canadian Institute of Mining, Metallurgy and Petroleum, Special Volume 53, pages 209-220.
Bowles, O. (1956): Granite as Dimension Stone, U.S. Bureau of Mines, Information Circular 7753, 18 pages.
Carr, G.F. (1955): The Granite Industry of Canada, Department of Mines and Technical Surveys, Number 846, pages 159-186.
Dolley, T.P. (2001): Dimension Stone; in Mineral Industry Surveys, U.S. Geological Survey, pages 74.1-74.11.
Gunning, D.F. (1998): British Columbia`s Industry Benefiting From Investment, Dimensional Stone, Volume 14, Number 6, pages 20-24.
Gunning, D.F. (1996): Market Study of Dimension Stone in the Western United States, unpublished report for British Columbia Trade Development Corporation, 121 pages.
Gunning, D.F. (1995): Exploring British Columbia`s Stone Industry, Stone World, October 1995, pages 40-50.
Harben, P. and Purdy, J. (1991): Dimension Stone Evaluation from Cradle to Gravestone; Industrial Minerals, February 1991, pages 47-61.
Nantel, S. (1984): L`Industrie de la Pierre de Taille au Quebec: Aspects Geologiques des Exploitations de Granite; in Guillet, G.R. and Martin, W., The Geology of Industrial Minerals in Canada, The Canadian Institute of Mining and Metallurgy, Special Volume 29, pages 70-78.
Parks, W.A. (1917): Building and Ornamental Stones of Canada, Volume 5, Province of British Columbia, No. 452, Canada Department of Mines, 233 pages.
Page, J.W. (1989): British Columbia Dimension Stone Market Study, unpublished report for the B.C. Ministry of Energy, Mines and Petroleum Resources, 49 pages.
Power, W.R. (1994): Stone, Dimension; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 981-1001.
Rodgers, M.C. (1995): Dimension Stone; in Rogers, M.C., Thurston, P.C., Fyon, J.A., Kelly, R.I. and Breaks. F.W., Descriptive Mineral Deposit Models of Metallic and Industrial Deposit Types and Related Mineral Potential Assessment Criteria; Ontario Geological Survey, Open File Report 5916, pages 139-142.
Shadmon, A. (1989): Stone. An Introduction, Intermediate Technology Publications Ltd, London, UK, 139 pages.
Simandl, G.J. and Gunning, D.F. (2002): Dimension and Ornamental Stone in British Columbia; in Dunlop, S. and Simandl, G.J., Editors, Industrial Minerals in Canada, Canadian Institute of Mining, Metallurgy and Petroleum, Special Volume 53, pages 21-25.
Springstead, S. (1995): Across the Canadian Border, Stone Companies Continue to Develop, Stone World, October 1995, pages 32-38.
Vagt, O. (2002): Stone; in Canadian Minerals Yearbook 2000, Natural Resources Canada, pages 51.1-51.15.
White, G.V. (1987): Dimension Stone Quarries in British Columbia; in Geological Fieldwork 1986, B.C. Ministry of Energy, Mines and  Petroleum Resources, Paper 1987-1, pages 309-344.
Zdunczyk, M.J. (2002): Dimension Stone: Fact, fiction, fractures, fickled and future, North American Mineral News, Metal Bulletin PLC,  Issue 83, April 2002, pages 9-12.

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Dimension Stone - "Marble"

R04
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

Hora, Z.D. (2007): Dimension Stone "Marble", in Selected British Columbia Mineral Deposit Profiles.

 

IDENTIFICATION

 

SYNONYMS: Commercial term “marble” includes all carbonate-rich sedimentary and metamorphic rocks that are suitable for dimension stone, such as limestone, crystalline limestone, dolomite or marble.

 

COMMODITIES (BYPRODUCTS): Marble blocks (lime or cement rock, aggregate, rip-rap and white fillers).

 

EXAMPLES  (British Columbia -  Canada/International):  Marblehead (082KSE076), Lardeau (082KSE077), Anderson Bay (092F 088), Hisnit Inlet (092F 020); Tyndall stone (Manitoba), Bruce Peninsula (Ontario), Saint-Marc-des-Carrieres (Quebec), Pittsford District (Vermont, USA), Sylacauga (Alabama, USA), Tate District (Georgia, USA), Yule Creek (Colorado, USA), Takaka Hill (New Zealand), Carrara (Italy), Thassos, Attica, Argolis (Greece), Spain, Portugal.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Marble dimension stone deposits occur in recrystallized/metamorphosed limestone or dolomite, where a general lack of joints makes the recovery of large blocks feasible. The marble should take a good polish and have an aesthetically pleasing colour and texture. Some metamorphosed limestones are suitable for dimension stone and are referred to as “marble” by the stone industry.

 

TECTONIC SETTINGS: Continental shelf and subsiding marginal marine basins and island arc environments.

 

DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: Subtropical and tropical shallow sea environments. Slightly magnesian limestone, is the typical carbonate sediment; dolomite is rather uncommon. Original limestone is frequently aragonite, later recrystallized into calcite. Most of dolomite is secondary, magnesium being introduced during lithification, diagenesis and regional hydrothermal dolomitization. Both rocks become parts of folded, faulted and thrusted, sometimes metamorphosed and recrystallized geological units as parts of orogenic belts and uplifted, exposed platform sediments.

 

AGE OF MINERALIZATION: Late Proterozoic to Mesozoic, some limestones may be Tertiary.

 

HOST/ASSOCIATED ROCKS: Depends on tectonic setting. In an island arc environment, the associated rocks are frequently a variety of volcanic, usually more mafic rocks and tuffaceous sediments, and sedimentary rocks, often greywacke, sandstone and argillite, with or without chert. Where metamorphosed, these rocks become schists, slates, gneisses and quartzites. Limestone may be contaminated by a tuffaceous component and form very colourful varieties. Higher metamorphic grades may result in skarn mineralogy. In a continental shelf setting, the volcanic component is usually missing and the associated rocks are argillites, sandstones, greywackes and the occasional conglomerate.

 

DEPOSIT FORM: The metamorphosed carbonate deposits are stratiform, may be folded, and may have gradational contacts. The thicknesses of mineable marble deposits range from 10 metres to several hundred metres.  Marble deposits commonly extend more than a hundred metres along strike; often individual deposits are parts of continuous carbonate belts (like in the Appalachian belt from Vermont to Alabama).

 

TEXTURE/STRUCTURE: Bedded with compositional and colour layers. Some marbles display complexly folded bedding or breccias that can enhance their appearance. In metamorphic marbles, the carbonate is so thoroughly recrystallized that much, or even all of the sedimentary features, are obliterated and replaced with an interlocking, mosaic texture. Highly metamorphosed varieties may exhibit features indicating a plastic flow, where original layering may be stretched or pulled apart and highly deformed. The limestones and weakly metamorphosed varieties may contain fossils and retain biological textures. In some deposits, fractured carbonate has been re-cemented to form a healed breccia texture.

 

ORE MINERALOGY [Principal and subordinate]: Calcite and dolomite.

 

GANGUE MINERALOGY [Principal and subordinate]: A large group of minerals that affect the processing and final appearance – some are harder than calcite or dolomite and result in elevations on a polished surface (chert, other forms of silica, silicate minerals like garnet and spinel, pyrite). Others are softer, or with well-developed cleavage, that results in hollows (graphite, phlogopite, chlorite, talc, tremolite, wollastonite, brucite). Some prevent the stone from taking a good polish (clay, finely disseminated graphite and hematite). Some are easy to oxidize and stain (pyrite).

 

ALTERATION MINERALOGY:  Recrystallization due to metamorphism improves the stone’s ability to take a high polish and results in more massive beds, sometimes with enhanced colours and texture features. Soft minerals like clays may recrystallize into harder silicates that take a good polish. Secondary veining may cement the broken and fractured carbonate rock into attractive textured stone breccia. The metamorphic process may also totally remove the dark-coloured organic matter disseminated in original limestone or recrystallize it in the form of graphite.

 

WEATHERING: Solution weathering results in a variety of karst features, but may also produce semiprecious varieties like Mexican onyx, a banded form of aragonite precipitated from hydrothermal waters or from calcium-rich groundwater in karst areas.  Mexican onyx and other semiprecious varieties are sometimes included commercially under the term marble.  Marbles with a silicate component (tremolite, flogopite and garnet) might significantly deteriorate in durability and strength. The weathering of pyrite results in unsightly stains and further deterioration by sulphuric acid attacking the surrounding carbonate. Exposure to salty air in coastal areas and smog in the cities frequently results in a rapid loss of luster on exposed polished marbles. Frequently, a weathered surface of the outcrop can indicate presence of impurities and their impact on stone quality.

 

ORE CONTROLS: The basic ore control is rock of suitable composition, attractive colour and consistent appearance. The frequency of bedding planes and transversal jointing determines the waste to ore ratio and the economics of production. In some regions, quarries are developed only in thickened beds near fold hinges.

 

GENETIC MODELS:  Most limestone of economic importance were partly or wholly biologically derived from seawater and accumulated in a relatively shallow, subtropical and tropical marine environment. Calcium carbonate producing organisms, such as corals, algae and mollusks can build reef structures hundreds of kilometres long and kilometres wide.  Limestones that form in a high-energy environment have more probability to be high-purity carbonate rocks.  Very fine carbonate muds, sometimes contaminated with clay-sized particles of silica and silicate minerals, accumulate in a low-energy environment of lagoons and deep water.  Under some specific conditions, original calcium carbonates may be enriched in magnesium, thus transforming original limestone into dolomite.  Under both regional and contact metamorphism, carbonate rocks recrystallize, sometimes reacting with internal contaminants to form a new suite of minerals.  Such recrystallization may result in a significant improvement of aesthetic appeal to the end user in resulting colour, structure and texture.  Both contact and regional metamorphism may remove black or dark grey organic substances resulting in highly prized pure white carbonate.

 

ASSOCIATED DEPOSIT TYPES: Limestone (R09), sandstone (R06), skarns (K01 to K09), travertine (H01).

 

COMMENTS:  So called “green marble”, or “Verde Antico”, of Italy and Greece in particular, is a variety of serpentine, classed commercially as a marble. Under low metamorphic conditions, peridotites and related rocks may produce bright green serpentinite, which has been used as a building and ornamental stone since ancient times. 

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: High-purity marbles will consist almost exclusively of calcite or dolomite  and contain only very minor amounts of other elements. 

 

GEOPHYSICAL SIGNATURE: Resistivity methods can outline karst features in covered terrain.

 

OTHER EXPLORATION GUIDES: Favourable marble beds are commonly found in belts of regionally metamorphosed sedimentary rocks or adjacent to a specific suite of intrusions, which have thermally metamorphosed carbonate beds.  Massive beds exposed along valley slopes and in natural cuts and outcrops.  Green “marble” in serpentinite belts, usually parts of accreted ophiolitic oceanic crust. 

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Canada and United States produce annually close to 500,000 tonnes of ornamental limestone and marble. Approximately 40 production centres are scattered over the continent, in at least ten states and three provinces. Commercial stone must meet ASTM specifications for its intended use.

 

ECONOMIC LIMITATIONS: “Marble” may be not attractive economically when dolomite forms thin layers in calcite because of different hardness and usually difference in grain size when dolomite is significantly finer grained than calcite. Waste to commercial size block ratio – depending on the type of quarry, waste should normally not surpass 25 to 30% of mined material. This may be higher if there is a market for the rejected material, for example, white limestone, which can be processed into calcium carbonate fillers, landscaping chips, etc. Limestone and marble in particular, are very sensitive to blast shock; therefore, in marble deposits the use of blasting must be avoided entirely. Also the mineral composition – presence of some deleterious minerals may be a limiting factor on the end use and restrictive to potential end uses. Minor components, like pyrite and other easily oxidized minerals, can stain marble when installed in some environments. Hard inclusions like chert nodules, silica veinlets, intrusive sills and dikes can make the marble difficult to process into a quality product and/or lead to differential weathering. Common types of marble can be produced and processed for a local market only; special varieties (coloured, snow-white) can travel globally.  Marble deposits have been successfully quarried underground throughout history. Marble deposit production in British Columbia has partly been quarried both from open pit quarries and underground. Modern methods using chainsaws and wiresaws have simplified removing blocks from underground quarries.

 

END USES: Marble tile, facing sheets, monumental stone, statues, fillers for paper and plastics, soil conditioner.

 

IMPORTANCE: Marble has provided structural, building and ornamental stone for millennia.  Many historical landmarks, artwork, buildings and structures used marble or limestone.

 

REFERENCES

 

Alseth, J. (1995): Current Thoughts on Stone Testing, Dimensional Stone, Volume 11, Number 10, pages 25–62.

Barker, J.M. and Austin, G.S. (1994): Stone, Decorative; in Carr, D.D., Senior Editor Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 367–378.

Bowles, O. (1939): The Stone Industries, 2nd Edition, New York, McGraw-Hill, pages 168–229.

Bowles, O. (1956): Limestone and Dolomite, United States Bureau of Mines, Information Circular  7738, 29 pages.

Bowles, O. (1958): Marble, United States Bureau of Mines, Information Circular 7829, 31 pages.

Bates, R.L. (1969): Geology of Industrial Rocks and Minerals; Dover Publications, Inc., New York, 459 pages.

Currier, L.W. (1960): Geologic Appraisal of Dimension Stone Deposit, United States Geological Survey, Bulletin 1109, 78 pages.

Harben, P. and Purdy, J. (1991): Dimension Stone Evaluation from Cradle to Gravestone, Industrial Minerals, February, pages 47–61.

Parks, W.A. (1912): Report on the Building and Ornamental Stones of Canada, Volume 1,Canada Department of Mines, Number 100, 376 pages.

Parks, W.A. (1917): Report on the Building and Ornamental Stones of Canada, Volume.V, Canada Department of Mines, Number 452, 233 pages.

Power, W.R. (1994): Stone, Dimension; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 987–1001.

Shadmon, A. (1989): Stone. An Introduction, Intermediate Technology Publications Ltd., London, United Kingdom, 139 pages.

Vagt, O. (1999): Stone; in Canadian Minerals Yearbook, Minerals and Metals Sector, Natural Resources Canada, pages 51.1–51.14.

White, G.V. (1987): Dimension Stone Quarries in British Columbia; in Geological Fieldwork 1986, BC Ministry of Energy, Mines and Petroleum Resources, Paper 1987-1, pages 309–344.

Zdunczyk, M.J. (2002): Dimension Stone: Facts, fiction, fractures, fickled and future, North American Mineral News, Metal Bulletin PLC, Issue 83, April 2002, pages 9–12.

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Dimension Stone - Andesite


R05
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

Originally a R05 profile was planned, but R03 covers this deposit profile (ZDH, DVL; 2009).

 

Dimension Stone - Sandstone


R06
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

IDENTIFICATION

 

SYNONYMS:  Bluestone, brownstone, freestone, arkose, greywacke, quartzite.

 

COMMODITIES (BYPRODUCTS):  Building stone.

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):   Newcastle Island (092GSW022), Gabriola Island (092GSW021), Saturna Island (092B 068), Denman Island (092F 426), Jack Point (092GSW049),Koksilah (092B 122); Paskapoo sandstone, Alberta; Nepean sandstone, Ontario; Wallace sandstone, Nova Scotia; Potsdam sandstone, New York; Ohio sandstone, Ohio; UK, France, Germany.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONUniform massive beds of sandstone with very few and well spaced (over 1 metre) fractures and bedding planes. Sandstone must be suitable to be removed from a quarry face in square shaped blocks that are 10 tonnes or larger with minimum waste. Some sandstones may be feldspathic (arkose) or with prominent dark component (greywacke).

 

TECTONIC SETTINGS: Shallow marine or lacustrine basins, tectonically rather quiet with wide spread uplift or downthrust events. 

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTINGShallow continental shelf, inland sea or  large continental lacustrine basins with low energy environment and a steady supply of well sorted, detrital, sand size particles. The mineral composition is influenced by the regional climate over the source area; speed, type and intensity of weathering and speed of transportation into the sedimentary basin.

 

AGE OF MINERALIZATIONAny age. Dimension stone sandstones are known to be of Cambrian, Carboniferous, Permian, Triassic, Cretaceous and Tertiary ages.

 

HOST/ASSOCIATED ROCK TYPES:  Sandstone beds are part of sedimentary sequences, which may include shale, siltstone, greywacke, limestone and conglomerate. Coal may be associated with sandstone beds. Limestone beds in sandstone sequences are rather uncommon.

 

DEPOSIT FORMMassive beds of thickness more than 1 metre, may be layered or cross bedded, uniform in appearance. Deposits commonly extend over areas of at least several square kilometers. Usually the deposits are horizontal or tilted, rarely folded.

 

TEXTURE/STRUCTURE:  Sandstones possessing uniform grain size and a massive, inconspicuous cementing matrix; they can exhibit bedding and cross bedding features. In outcrop the stone has a smooth surface with very few irregularities which would result from preferential weathering, either due to inhomogeneous composition or the presence of microfractures.

 

ORE MINERALOGY [Principal and subordinate]Quartz, feldspar, volcanic rock fragments; clay, ferrous and ferric oxides, chlorite, mica, calcium carbonate, detrital coal.

 

GANGUE MINERALOGY [Principal and subordinate]: Clay, silt and mica layers, wispy coal layers, conglomerate; pyrite, phosphatic nodules, fossil shells.

ALTERATION MINERALOGYWeathering of the sandstone can change ferrous ions into ferric iron staining or overall colour change. Feldspathic component may alter into a variety of clay minerals.

 

WEATHERING:  Sandstone weathering may result both in physical and chemical deterioration. High porosity sandstones are sensitive to freeze – thaw activity resulting in exfoliation and surface erosion. Chemical deterioration may affect cementing matrix (carbonate leaching), oxidation of some components (pyrite) with resulting rusty stains and soluble salts leaching out of the stone and precipitated as white stains on the surface or enhancing exfoliation activity. Most common weathering effect, even in the best quality sandstones is changing  the bluish colour of fresh stone into beige or brown as a result of oxidation of ferrous component into ferric. This change does not have to affect the physical durability of the stone. 

 

PRODUCT CONTROLS:  The primary control is the presence of thicker sandstone beds. Secondary controls are absence of significant deformation and limited amounts of other rock types.


GENETIC MODELShallow continental shelf or inland sea or large lacustrine basin with low energy environment and a steady supply of well sorted clastic material. After the deposition, the accumulated sediment has to be cemented either by a chemical process (usually carbonate or silica) or by a physical compaction.

 

ASSOCIATED DEPOSIT TYPES:  Cement shale (R01), expanding shale (R02), coal (A03, A04, A05), silica sandstone/quartzite (R07).

 

COMMENTS:  In British Columbia, sandstone as a building stone was replaced in part by so called “Haddington Island andesite”, which has very similar look, but much better physical properties and durability. Sandstones are in general not suitable for polishing and are used with rough or just plain cut surface. Only some quartzites may have potential for polished ornamental stone products (Babette Lake quartzite). Use of sandstone in Canada and North America in particular is very limited, quarried mostly for maintenance and repairs of heritage structures.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATUREHigh silica contents and low aluminosilicate and carbonate contents.

  

GEOPHYSICAL SIGNATURE Resistivity can identify fracture density and bedding features in areas of insufficient outcrops, also the presence of clay layers and their frequency can be established. Shallow seismic can identify inhomogeneities in the deposit – like shale layers, weakly cemented beds and different lithologies.

 

OTHER EXPLORATION GUIDES:  Large smooth bedrock exposures in cuts, on valley slopes and along shorelines lacking fragmented rock are good indicators. An air photo study can identify large outcrop areas and boulder fields.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  Required properties, standard specifications for stone used in construction and industrial applications, are listed in ASTM (American Society for Testing Materials) designations, particularly C616. Production volumes in North America are relatively small, in 1998 dimension sandstone production in USA was reported to total 185,000 tonnes, coming from 30 production centers, with value of approximately US$ 80 per metric tonne. In Canada, six provinces in 1999 produced 47,000 tonnes, with value of CDN$ 125 per metric tonne. 

 

ECONOMIC LIMITATIONS:  The frequency of joints, structural and textural inhomogeneities, presence of shale interbeds and abundance of irregular and oblique shape fractures are all features that increase waste and affect the volume of sandstone needed to be removed in recovering square 10 to 20 tonnes blocks. Economic deposits can afford a maximum of 25 to 30 % of waste. The price per metric tonne does allow for only a minimum waste to saleable block ratio. The presence of some undesirable minor components like pyrite can produce unsightly stains if in contact with moisture that diminish the desirability and value of a particular stone. Susceptibility to an increased rate of deterioration due to smog in the cities or salty air in coastal areas tends to reduce sandstone demand in such areas. Transportation is a major cost factor in reaching more distant markets.

 

END USES: Sandstone is a traditional building stone in many parts of Europe and elsewhere. Originally it was used as ashlar and construction blocks, lintels, sills, door and window frames and grinding wheels. Presently sandstone is utilized mostly for maintenance and repair of heritage buildings, paving and wall facing sheets and ashlar.  Flagstone is a common substitute.

 

IMPORTANCE:  In the past a very important structural material, replaced in the 20th century by more durable


materials. Important stone used for restoration, repairs and maintenance of heritage structures.

 

REFERENCES

  

Barton, W.R. (1968): Dimension Stone. U.S. Bureau of Mines, IC8391, 147 pages.

Bowles, O. and Barton, W.R. (1963): Sandstone as Dimension Stone. U.S. Bureau of Mines, IC 8182, 30 pages.

Burwash, R.A., Cruden, D.M. and Mussieux, R. (2002): The Geology of Parliament Buildings 2. The Geology of the Alberta Legislative Building. Geoscience Canada, Vol.29, No.4, page 139-146.

Currier, L.W. (1960): Geologic Appraisal of Dimension Stone Deposit. U.S. Geological Survey, Bulletin 1109, 78 pages.

Dolley, T.P. (1999): Stone, Dimension; in Mineral Industry Surveys, U.S. Geological Survey, pages 73.1-73.10.

Harben, P. and Purdy, J. (1991): Dimension Stone Evaluation. From Cradle to Gravestone. Industrial Minerals, Number 281, pages 47 – 61. 
Lawrence, D.E. (2001): Building Stones of Canada`s Federal Parliament Buildings. Geoscience Canada, Volume 28, Number. 1, pages 13-30.

Mustard, P.S. (1994):  The Upper Cretaceous Nanaimo Group, Georgia Basin; in Geology and Geological Hazards of the Vancouver Region, Southwestern British Columbia, Monger, J.W.H., Editor, Geological Survey of Canada, Bulletin 481, pages 27-96.

Parks, W.A. (1917): Report on Building and Ornamental Stones of Canada, Volume V., Province of British Columbia. Canada Department of Mines, No. 452, 233 pages.

Power, W.R. (1994): Stone, Dimension; in Industrial Minerals and Rocks, Carr, D.D., Senior Editor, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, page 987 – 1001.

Shadmon, A. (1989): Stone. An Introduction. Intermediate Technology Publications Ltd., London, U.K., 139 pages.

Vagt, O. (1999): Stone; in Canadian Minerals Yearbook, Minerals and Metals Sector, Natural Resources Canada, page 51.1 – 51.14.

White, G.V. (1988): Sandstone Quarries Along the Strait of Georgia; B.C. Ministry of Energy, Mines and Petroleum Resources, Geological Fieldwork 1987, Paper 1988 – 1, pages 385-392.

Zdunczyk, M.J. (2002): Dimension Stone: Facts, Fiction, Fractures, Fickled and Future, North American Minerals News, Metal Bulletin PLC, Issue 83, April 2002, pages 9-12.

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Silica-rich Rocks

R07
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: High silica quartzite, quartz sandstone, silica rock silicastone.

 

COMMODITIES: Silica sand, lump silica.
 

EXAMPLES (British Columbia (MINFILE #) - Canada/International)Golden (082N001), (082N043), Longworth (093H038), Bridesville (082ESW144) – Selkirk, Manitoba, Badgley Island, Ontario, St. Canut, Quebec; Oriskany sandstone, Pennsylvania and West Virginia, St.Peter sandstone, Illinois and Missouri.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONUniform, massive beds of siliceous sediments, such as sandstone and chert, or their metamorphic equivalents, like quartzite. These beds are commonly formed in sedimentary sequences, although some cherts can be found with volcanic  rocks. They have high silica contents with very limited impurities, usually under 1%.

 

TECTONIC SETTINGSSiliceous sediments formed on a shallow continental shelf or deposited in inland seas, large lacustrine basins or rift zones on the continent. Cherts form in oceanic environments associated with island arcs and spreading centers. Quartzites found in orogenic belts of all ages.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTINGSiliceous sediments deposited into a low energy environment slowly sinking or stagnant sedimentary basin.  Source area has to be rich in siliceous sedimentary, igneous or metamorphic rocks to provide a steady supply of well sorted and weathered clastic material to estuaries along the shoreline.  Weathering conditions before and during transportation should be able to separate resistant quartz from less stable feldspars, hornblende and pyroxenes, transporation will separate the clay minerals and mica with heavy minerals from the silica particles.  Cherts form in oceanic environments near and distal to spreading centres and rift zones and along volcanic belts as exhalative deposits.  They can also form as biogenic and/or chemical precipitates of selica gel in an oceanic environment.


AGE OF MINERALIZATION:  Precambrian to Tertiary. modern protolithic facies on the seafloor.


HOST/ASSOCIATED ROCK TYPESSiliceous sediments are found with a wide spectrum of clastic and carbonate rocks, including coal and associated with clay deposits. Cherts are found with felsic to mafic and ultramafic volcanics and associated greywacke and shale. Quartzites and metamorphic cherts are found with the metamorphic equivalents of the rocks listed previously.


DEPOSIT FORM: The siliceous sediments occur as metres thick beds that can extend more than tens of kilometres, while the chert beds may be up to several tens of metres thick and laterally extend for hundreds of metres but are frequently discontinuous. 

 

TEXTURE/STRUCTURESilica-rich sediments typically have uniform grain size, may be well lithified or friable, and can be layered, cross bedded or massive beds. Massive or rhythmically bedded chert is found sometimes with argillaceous interbeds and soft sediment deformation features. Quartzites as metamorphosed equivalents of sandstones or cherts usually display the structure of the original rock.


ORE MINERALOGY [Principal and subordinate]:  Quartz; chert can also have other forms of amorphous and microcrystalline silica.


GANGUE MINERALOGY [Principal and subordinate]Siliceous sediments can contain clay minerals, pyrite, mica and minor heavy minerals (rutile, sphene, ilmenite, zircon, etc.). Cherts can contain clay minerals, hematite, manganese oxides, pyrite; rhodonite, rhodochrosite, calcite, barite.


ALTERNATE MINERALOGY: Fractures can have secondary Fe - Mn hydroxides and/or calcium carbonate. 


WEATHERING:  Usually weather resistant, resulting in morphological highs.  Only some friable sandstones result in depressions.  

 
ORE CONTROLS: Source terrains that minimize impurities and despositional environments that includes long or repeated transportation with intensive wear of particles which includes separation from other silicates like feldspars for example.  This may occur both by physical as well as chemical weathering. 


GENETIC MODELSSiliceous sediments form on the shallow continental shelf and in inland seas or large lacustrine basins with a relatively low energy environment and a steady supply of well sorted silica sand. After the deposition, the accumulated sediment will be cemented by compaction, a minor clay component, or introduced secondary silica. Cherts form in deep water oceanic environment with hydrothermal activity and abundance of radiolarians suggest oceanic upwelling that enriches water in nutrients., or recrystallized under metamorphic conditions.

 
ASSOCIATED DEPOSIT TYPESSiliceous sediments - building stone; cherts - Sedex and VMS deposits, marine diatomite.

 


COMMENTS:  Crystalline silica in dust form is considered a carcinogenic health hazard.  Mineral processing of alaskite feldspar rocks can produce a very high purity (10 to 200 ppm impurities) silica co-product.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: In general more than 98% silica with traces of other elements.


GEOPHYSICAL SIGNATURE: Only where contrast with host rocks is significant.


OTHER EXPLORATION GUIDES:  Look for resistant ridges and outcrops and absence of impurities in hand sample visible to the naked eye. 

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  Each use has its very specific requirement for the particle size and shape, physical strength and permissible amounts of different impurities. For lump silica the concerns are purity, sizing of crushed rock (fracture and bedding density) and contamination by Ca, Fe, Mn, Ti, Al, Na and K minerals or graphite and silica sand  they are friability and size of silica particles and contamination by Fe, Mn and Al minerals and refractory minerals of Al, Zr, Cr. Generally silica contents have to be 98% with significant impurities removable by processing. Which depend on the end use. Even high purity orthoquartzite usually contains minute titanium minerals which are detrimental for silicon metal (even at 0.2% TiO2). Also, even trace of Ca can make silica unacceptable for specific end uses. Lasca grade silica may contain impurities in ppm only. Such contaminants may be absent in oceanic cherts. Individual deposits range from 1 million tonnes to 100 million tonnes.


ECONOMIC LIMITATIONSWhile some very specific silica raw materials may be relatively expensive, the basic types of silica sand or lump silica are low priced, bulk commodities sensitive to transportation costs. For its main uses, silica sand from sandstones has a number of substitutes and their use depends on local or regional availability. Silica is available as a co-product or by-product of feldspar and residual kaolin mining and is produced locally from dune and beach sands. Foundry sand can be substituted by some other minerals, like olivine, for example.


END USESMost silica is used in the form of sand to manufacture glass products and as foundry sand. In North America, about one third is used in glass and one-fifth as foundry sand. The remaining silica is divided among a multitude of metallurgical and chemical uses, including cement, ceramics, fillers and blasting sand. Very high quality silica is being used for a long list of synthetic silicas and silicon chemicals, silicon metal, ferrosilicon and silicon carbide, cultured silica crystals and silica glass. Silica sand for hydraulic fracturing has to be well rounded and to withstand very high pressures when pumped into oil and gas wells to enhance the recovery. The past widespread use of fine grained silica rocks was to make acid refractory bricks (dinas) used in iron metallurgy. These silica rocks were termed “dinas rock”.


IMPORTANCEIn the year 2000 Canadian production was 2.0 million tonnes and the United States produced 28.5 million tones annually. Cement, glass and ceramics are unthinkable without silica, so is the use as a foundry sand. Most of other applications are less visible, but equally important for industrial societies.

 

 

REFERENCES

 

 

Dolley, T.P. (2001): Silica; in Mineral Industry Surveys, U.S. Geological Survey, pages 67.1-67.19.

Dumont, M.  (2002): Silica; in Canadian Mineral Yearbook, Minerals and Metals Sector, Natural Resources Canada, pages 46.1-46.12.

Foye, G. (1987): Silica Occurrences in British Columbia, Open File 1987-15, B.C. Ministry of Energy, Mines and Petroleum Resources, 55 pages.

Harben, P.W. (1995): The Industrial Minerals HandyBook, Metal Bulletin PLC, London, UK, 253 pages.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals. A Global Geology, Metal Bulletin PLC, London, UK, 462 pages.

Heinrich, E. W.M. (1981): Geologic Types of Glass-sand Deposits and Some North American Representatives, Geological Society of America, Bulletin, Volume 92, pages 611-613.

Kendall, T. (2000): Written in Sand. The World of Specialty Silicas, Industrial Minerals, Number 390, Metal Bulletin PLC, London, UK, pages 49-59.

Loughbrough, R. (1993): Silica Sand. The Essential Ingredient; in Skillen, A.D. and Griffiths, J.B., Raw Materials for the Glass & Ceramic Industries, Consumer Survey, Metal Bulletin PLC, London, UK, pages 29-35.

Moore, M.A., Morrall, F.J. and Brown, R.C. (1998): Crystalline Silica Issues and Impacts for Industry, Industrial Minerals, Number 367, Metal Bulletin PLC, London, UK, pages 109-117.

Murphy, T.D. (1960): Distribution of Silica Resources in Eastern United States, U.S. Geological Survey, Bulletin 1072 – L, pages 657-665.

Zdunczyk, M.J. and Linkous, M.A. (1994): Silica. Industrial Sand and Sandstone; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 879-911.

 

 

 

Flagstone

R08
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Paving stone, facing stone, split stone.

 

COMMODITIES (BYPRODUCTS): Paving and wall cladding stone, ashlar, roofing slate as a co-product, (aggregate, landscaping stone). 

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  Nipple Mountain (082ENW109), Porcupine Creek (082FSW279), Sheep Creek (082FSW288), Revelstoke (082LNE025), McNaab Creek (092GNW009), Jervis Inlet (092JW029), Dome Creek (093H028), Beaverdell (082ESW169); Exshaw, Alberta; Coconino sandstone, Arizona; Pennsylvania Bluestone, Pennsylvania and New York.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONFlagstone is a rock, often sedimentary or metasedimentary, that splits into sheets and slabs with parallel sides due to bedding, schistosity, cleavage, planar weakness or natural jointing. Flagstone can be of any type of rock as long as it meets the basic requirements of soundness and resistance to abrasion and  weathering.

 

TECTONIC SETTINGSPractically any setting; type of lithified sediments , sand dunes, volcanosedimentary deposits, schistose metamorphic rocks, magmatic and volcanic rocks.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Clastic and chemical sediments and their metamorphic equivalents; intrusive and volcanic rocks and their tuffaceous equivalents.


AGE OF MINERALIZATION: Any age - Precambrian to Tertiary.


HOST/ASSOCIATED ROCK TYPES: Sandstone, siltstone, shale, carbonate rocks; quartzite, gneiss, schist, slate, marble; granitic rocks, rhyolite, phonolite and related tuffs (particularly zeolitized).


DEPOSIT FORMBedded or schistose unit which may be flat or steeply dipping. Plutonic bodies of intrusive rocks, lava flows. Deposits of flagstone are usually tens of metres thick by thousands of metres square.

 

TEXTURE/STRUCTURESedimentary and metasedimentary:  Bedded structure with absence of folding or other irregularities affecting flat surface.  Clastic sediments cemented by silica, calcium, calcium carbonate or by compaction.  Foliated metamorphosed equivalents with graphite or mica separating individual sheets.  Igneous:  Magmatic rocks may be equigranular or porphyritic.  More commonly the igneous rocks have a blocky or platy structure with large scale open folds, banded intrusives and flows with preferential parallel splitting.

 

ORE MINERALOGY [Principal and subordinate]: Rocks types that are resistant to weathering due to the presence of silicate and carbonate minerals and with lack of clays, sulphides and minerals susceptible to chemical or physical weathering, like cordierite and chlorite.

 

GANGUE MINERALOGY [Principal and subordinate]Clay and coaly wisps and layers, carbonate and siliceous nodules and veinlets, massive thick beds not splitting in a saleable product, different colour unhomogenities like black nodules and knots, beds or zones with minerals producing unsightly stains.


ALTERATION MINERALOGYClay minerals after feldspars, sericite, chlorite, zeolites.


WEATHERINGMicrofractures and presence of clay minerals may result in exfoliation. High porosity can be frost sensitive. Bi-valent iron component turns into tri-valent form, resulting in colour change from bluish-green into beige to brown. Common sulphides like pyrite and pyrrhotite, some biotite and other iron containing minerals oxydize, producing rusty stains and spots. Also the presence of soluble salts (chloride, sulphate or carbonate) in some rocks (mostly sandstones, but also limestones and siltstones) can result in unsightly staining and exfoliation.


PRODUCT CONTROLSFrequency of bedding planes to produce a standard thickness of the product, frequency of jointing to allow production of commercial size of sheets and shapes with minimum waste. Distribution and presence of deleterious minerals affecting the end use and durability of product in construction trades. Presence of unusable beds, like conglomerate in sandstone etc.


GENETIC MODELS:  Sandstone – beach and near shore clastic sediment in low energy environment, deltaic fans in shallow sea, aeolian deposits, diagenetically cemented by silica, limestone or by compaction. Quartzite may be the metamorphic equivalent. Laterally may grade into siltstone or silty limestone. Slate – a clayey, monotonous and uniform deep water sediment with well developed cleavage as a result of low grade metamorphism. Schist – fine grained clastic or clayey sediment highly metamorphosed  into the muscovite or biotite schist, where mica layers separate quartz-feldspathic sheets. Limestone – organic or inorganic sediment in a variety of marine environments, of bedded texture. .As flagstone frequently with many impurities, sometimes fossiliferous. Beds may be separated by clayey partings. Tuff – air-fall or waterlain, finegrained volcanic ash cemented by recrystalization, devitrification (zeolitization for example) or compaction.  Igneous rocks – medium to fine grained magmatic rocks, sometimes porphyritic, of massive or banded texture, with preferential splitting in sheets.

 
ASSOCIATED DEPOSIT TYPESSandstone - coal (A02, A03) , expanding shale, cement shale, dimension sandstone; slate - schist -  slate, quartzite, sandstone, limestone;  marble, industrial limestone (cement and lime, filler); zeolite, diatomite, bentonite, sedimentary kaolin; igneous rocks -  dimension granite, crushed aggregate.


COMMENTS:   

Some flagstones are produced by cutting or splitting large square blocks of sandstone, slate and granite. Roofing slate is a type of flagstone that splits into thin sheets.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATUREHigh silica, feldspar, mica, sometimes carbonates.


GEOPHYSICAL SIGNATURENot normally used. This is  very often a cottage type industry where economics do not allow expensive exploration methods.


OTHER EXPLORATION GUIDES:   

Good flagstone is indicated by large sheets of stone naturally exposed by physical weathering.

 

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGEFor many end uses the most important criteria is previous  performance. While there are ASTM specifications for a number of physical properties required in specific applications, many popular stones have never been thoroughly tested. Annual production in the USA is between 130,000 and 140,000 tonnes from some 50 main quarrying site. Established producers in British Columbia and Alberta were processing in the year 2000 approximately 17,500 tonnes a year from 13 sites.


ECONOMIC LIMITATIONSMost of the flagstone types are used in local or regional markets, and the use of some particular stone depends on the personal taste, or sometimes fashion. Also, local availability is an important factor for choosing one stone over another. Transportation cost has important role in distributing flagstone to more distant markets. Only few flagstones, of particularly attractive or a rather unusual colour or texture can reach far away destinations. Such products are for example so called “Pennsylvania Bluestone” from New York, red or green slate from Vermont, and “Tyndall Stone” dolomitic limestone from Manitoba.

 

 

REFERENCES

 

Barker, J.M. and Austin, G.S. (1994): Stone, Decorative; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 367 – 378.

Bowles, O. and Barton, W.R. (1963): Sandstone as Dimension Stone. U.S. Bureau of Mines, IC 8182, 30 pages.

Currier, L.W. (1960): Geologic Appraisal of Dimension Stone Deposit. U.S. Geological Survey, Bulletin 1109, 79 pages.

Dolley, T.P. (1990): Stone, Dimension; in Mineral Industry Surveys, U.S. Geological Survey, pages 73.1- 73.10

Hora, Z.D. (2003): Feldspathic Sandstone Flagstone from near Hudson Hope, Northern British Columbia - Potential for Sandstone Production in British Columbian; in Geological Fieldwork 2002, British Columbia Ministry of Energy and Mines, Paper 2003-1, pages 175-185.

Power, W.R. (1994): Stone, Dimension; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 987 – 1001.

Shadmon, A. (1989): Stone. An Introduction. Intermediate Technology Publications Ltd., London, U.K.., 139 pages.

Vagt, O. (1999): Stone; in Canadian Mineral Yearbook, Minerals and Metals Sector, Natural Resources Canada, page 51.1 – 51.14

 

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Limestone

R09
by Z.D. Hora

Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Limerock, cement rock, calcium carbonate.

 

COMMODITIES (BYPRODUCTS): Limestone (aggregate, rip-rap, white fillers).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  Blubber Bay (092F 397, 479), Lafarge Limestone (092F 396), Gillies Bay (092F 395), Imperial (092F 394), Bamberton (092B 005), Benson Lake (092L 295), Pavilion Lake (092INW081), Harper Ranch (092INE001), Lost Creek (082FSW307), Dahl Lake (093G 032), Ptarmigan Creek (093H 017); Palliser Formation Cadomin and Exshaw limestones (Alberta), Detroit River Group – Woodstock, Beachville (Ontario), Trenton Group – Joliette, Beauport, Saint-Constant (Quebec), Mississippian Monte Cristo limestone, Lucerne Valley, (California, USA), Ordovician Kimmswick limestone, Clarksville (Missouri, USA).

 

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Calcium carbonate sedimentary rock that occurs in beds, usually tens of metres thick, with or without minor dolomite.  High-grade limestone can be almost pure (less than 1.4% impurities for chemical lime).  Lowest grades of limestone (marlstone) can be used for cement with as little as 65% calcium carbonate, with contamination by finely disseminated clay and silica.  The limestone may be recrystallized by various degrees of metamorphic grade.  Marl and chalk are poorly lithified forms of limestone.
 

TECTONIC SETTINGS: Recent and Ancient continental shelf and subsiding marginal marine basins are the most common settings; island arc environments also important.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Subtropical and tropical shallow sea environment. Calcium carbonate, usually slightly magnesian, is the typical primary component; dolomite is rather uncommon. The original mineral is frequently aragonite, later recrystallized into calcite. During lithification and diagenesis, under a variety of geological processes, it may be partially or completely dolomitized (see R10).

 

AGE OF ROCK FORMATIONLate Proterozoic to Holocene, main producers globally are Paleozoic, Mesozoic and Tertiary.

 

HOST/ASSOCIATED ROCK TYPES: Shelf-deposited limestone beds are often found within thicker sedimentary sequences with associated dolomite, argillite, sandstone and intermediate sedimentary rocks. Island arc limestone often has a volcanic component, such as tuffaceous rocks, sills, submarine lava and palagonite breccia. Sometimes found in cherty layers and interbeds.

 

DEPOSIT FORM: Lenses, massive beds; folded and unfolded. Thickness of mineable limestone deposits range from ten to several hundreds of metres. The areal extent of some deposits covers hundreds of square kilometres.

 

TEXTURE/STRUCTURE: Massive, bedded, fine- to coarse-grained, sometimes with crossbedding features, sometimes porous, fossiliferous, with stylolites.  Interbeds with chert nodules.

 

ORE MINERALOGY [Principal and subordinate]: Calcium carbonate with minor dolomite, clay, shale and silica.  Some limestones may contain finely dispersed bitumen.

 

GANGUE MINERALOGY [Principal and subordinate]: All types of silicate rocks, chert, pyrite, intrusive dikes on Texada Island.


ALTERATION MINERALOGY: Groundwater dissolution results in karst cavities, which are frequently filled with clay.  Metamorphism recrystallizes the limestone and mobilizes the dispersed bitumen, which can remain as graphite.  With high metamorphic grades, clay and silica will recrystallize into skarn-like groups of silicate minerals and crystalline silica.

 

WEATHERING: Solution weathering results in a variety of karst landforms in most climatic areas, but intensifies with a warmer climate. Most intensive karstification may produce deposits of bauxite.

 

ORE CONTROLS: Favourable limestone units often occur in belts that reflect original depositional environments.  Limestone very often forms well-defined stratigraphic and lithological units.  Horizontally, limestone will grade gradually into impure limestone and other sedimentary facies, which will reduce the value depending on the end use due to the changes in chemical composition and quantity and type of contaminants.  Highly sought white limestone for mineral fillers is usually a product of the contact or regional metamorphic processes.


GENETIC MODEL: Most limestone deposits of economic importance were biologically derived from seawater as detrital calcium carbonate and accumulated in a relatively shallow marine environment.The other form is by organic framebuilders like coral and algae as local and regional reef structures. The environment of deposition determines the size, shape and purity of the carbonate rock.

 

ASSOCIATED DEPOSIT TYPES: Deposits of dolomitic limestone and dolomite (R10), marble building stone (R04).

 

COMMENTS: A relatively small percentage of limestone contains alumina and other oxides in the right proportions to make cement and are termed "cement rock".  Recrystallization of limestone may have a significant effect on the limestone use.  Particularly coarse crystalline rock may decrepit during calcinations and make the rock unusable in rotary and vertical kilns.  In some African countries, carbonatites are used in the absence of sedimentary limestone to manufacture both cement and lime.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: High CaCO3 content.

 

GEOPHYSICAL SIGNATURE: Resistivity has been used to identify karst features in covered terrain.


OTHER EXPLORATION GUIDES: Regional belts of sedimentary rocks with limestone potential are the primary exploration tool. Karst topography and underground streams indicate carbonate units.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Limestone is an extremely versatile industrial rock processed into many end products. Diverse uses have diverse quality requirements, controlled by specifications on chemical composition, physical properties, local availability and consistency. Some specifications deal with the final product and may be controlled during processing (for example, cement). Other end uses require exact limits in composition or physical properties. There are numerous ASTM standards and industry specifications defining a typical grade for each particular application.

 

The main global limestone uses are cement and lime manufacturing. In 2000, the U.S. produced 15 million tonnes of lime and 83 million tonnes of cement. In the same year, the U.S. imported 25 million tonnes of cement and 113 thousand tonnes of lime.

 

A typical cement plant in developed countries has a capacity of approximately 1 million tonnes annually, while a typical lime plant will produce between 100 and 200 thousand tonnes of lime per year. Because high-grade limestone contains 44% carbon dioxide, a plant requires almost 2 tonnes of limestone for every tonne of product.


In many regions, where rocks of magmatic origin are absent, fine-grained, unmetamorphosed limestone and dolomite are the most common source of crushed, quarried aggregate. Some of these types of stone products can be a source of extremely undesirable alkali-aggregate reactivity. Such reactivity may result in early deterioration of concrete structures.

 

In filler application, a calcium carbonate and dolomite mix is extremely undesirable due to the difference in hardness.  For many applications, paper in particular, the presence of dolomite contamination ruins the product.

 

ECONOMIC LIMITATIONS: In some regions, limestone is mined by underground methods even for uses such as cement production.  Limestone used for paper and fillers requires a high brightness (over 90GE), chemical purity, absence of hard minerals like quartz and absence of graphite or other colour components.  For high-end uses, flotation to remove deleterious components is routine.  Lime is produced from limestone with high calcium carbonte (>9597%) and low MgO (<5%) contents.  The rock must not decrepitate in the kiln during calcination.  Cement normally contains <6% MgO and <0.6% Na2O + K2O in the final product. Transportation is frequently a major cost

 

of the finished product. Limestone quarries operate near many cities; limestone products often travel longer distances to markets.  For example, white filler-grade limestone in Washington State is shipped by rail some 600 kilometres from the quarry to the processing plant. Lime-grade limestone from Texada Island is barged to coastal users from Alaska to northern California. Cement is imported to many coastal points in the United States from overseas.  

 

END USESCement, lime, soil conditioner, glass, fillers, fluxing agent, acid neutralization. Some limestone is used for dimension stone and is discussed in profile R04.

 

IMPORTANCE: This deposit type accounts for virtually all production of cement and lime in North America.

 

SELECTED BIBLIOGRAPHY

 

Ames, J.A., Cutcliffe, W.E. and Macfadyen, J.D. (1994): Cement and Cement Raw Materials; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration Inc., Littleton, Colorado, pages 296-216.

Carr, D.D., Rooney, L.F. and Freas, R.C. (1994): Limestone and Dolomite; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks: Society for Mining, Metallurgy and Exploration Inc., Littleton, Colorado, pages 605–629.

Bates, R.L. (1969): Geology of Industrial Rocks and Minerals; Dover Publications Inc., New York, 459 pages.

Bathurst, R.G.C. (1975): Carbonate Sediments and Their Diagenesis; Elsevier Scientific Publication Company, New York, 658 pages.

Bowles, O. (1956): Limestone and Dolomite; U.S. Bureau of Mines, IC 7738, 29 pages.

Fischl, P. (1992): Limestone and Dolomite Resources in British Columbia; BC Ministry of Energy, Mines and Petroleum Resources, Open File 1992-18, 150 pages.

Harben, P.W. (1995): The Industrial Minerals HandyBook; Metal Bulletin PLC, London, UK, 253 pages.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals, A Global Geology, Metal Bulletin PLC, London, UK, 462 pages.

Malhotra, V.M., Program Principal (1991): Petrography and Alkali-Aggregate Reactivity; Course Manual, CANMET, Energy, Mines and Resources Canada, 509 pages.

Miller, M.M. (2001): Lime; in Mineral Industry Surveys, U.S. Geological Survey, pages 40.1­40.15.

Soles, J.A., Editor (1990): International Workshop on Alkali-Aggregate Reactions in Concrete; Occurrences, Testing and Control, Proceedings, CANMET, Energy, Mines and Resources Canada, 386 pages.

Van Oss, H.G. (2001): Cement; in Mineral Industry Surveys, U.S. Geological Survey, pages 17.1­17.19.

Vagt, O. (2002): Cement; in Canadian Mineral Yearbook 2000, Minerals and Metals Sector, Natural Resources Canada, pages 14.1­14.8.

Vagt, O. (2002): Lime; in Canadian Mineral Yearbook 2000, Minerals and Metals Sector, Natural Resources Canada, pages 29.1–29.7.

Dolomite

R10
by Z.D. Hora

Retired, British Columbia Geological Survey, Victoria, B.C., Canada

IDENTIFICATION

 

SYNONYMS: Dolostone, dolomitite, dolospar.

 

COMMODITIES (BYPRODUCTS)Dolomite (aggregate, filler). Sometimes dolomite may be a byproduct of quarrying limestone.

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International)Crawford Creek (082FNE113), Pilot Point (082FNE075), Oro Viejo (082M 254), Rock Creek (082ESE200), / Gunton, Stonewall, Stony Mountain (Manitoba), Guelph, Bruce Peninsula (Ontario), Portage-du-Fort, Havre-Saint-Pierre (Quebec), Kelly Cove (Nova Scotia), Addy, Keystone (Washington), St.Paul, Minneapolis (Minnesota), Thornton, Joliet, Kankakee (Illinois),York (Pennsylvania),Sussex and Somerset Co. (New Jersey) USA; United Kingdom; Italy; France.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONA bedded or massive carbonate sedimentary rock that occurs as tabular bodies concordant with stratigraphy and beds up to tens of metres thick and zones controlled by faults and permeable zones. Dolomite contains more than 90% of the mineral dolomite and is usually a finely crystalline and slightly porous rock. Calcite is the most common other mineral.


TECTONIC SETTINGSDolomite is more common in Recent and Ancient continental shelf and subsiding marginal marine environment, however, economically attractive deposits also occur in island arc environments.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTINGDolomite is most common as a secondary replacement of marine sediments that were a slightly magnesian calcium carbonate that was frequently aragonite originally and later recrystallized into calcite. Circulating ground water (sea water, hypersaline brine, pore water) containing magnesium reacted with the calcium carbonate to produce dolomitic limestones and dolomites.  Dolomite may also form as a primary sediment, but this is not very common.

 

AGE OF MINERALIZATIONDolomite can be any age, but the ages of dolomitization for secondary deposits often are not well defined. Large scale regional dolomitization in western Canada has been linked to fluid circulation taking place during Devono-Mississippian and late Cretaceous-Tertiary periods.   Generally these deposits are believed to be concurrent with large scale tectonic activity.

 

HOST/ASSOCIATED ROCK TYPES:  Dolomites are often found within thicker sedimentary sequences with associated limestones, dolomitic limestones, argillites, sandstones and evaporates. In island arcs, dolomites often have a volcanic component, such as tuffaceous rocks, sills, submarine lavas, palagonite breccias and sometimes cherty layers and interbeds.

 

DEPOSIT FORM:  Large tabular bodies concordant with stratification that may be up to several tens of metres thick and extend for hundreds to thousands of metres. There are also regional nonconformable dolomitized zones, sometimes controlled by faults and by permeability of both the host and adjacent sedimentary units.

 

TEXTURE/STRUCTURE:  Finely to medium grained, crystalline, sucrosic texture, sometimes retaining textures like fossils and laminations of original limestone. Solution-collapse breccias and replacement zones are usually a medium grained, white, granular texture.

 

ORE MINERALOGY [Principal and subordinate]:  Dolomite / quartz, brucite, calcite, chert, kaolinite, illite, sometimes bitumen.

 

GANGUE MINERALOGY [Principal and subordinate]Limestone and dolomitic limestone.


ALTERATION MINERALOGY:  Dolomite is typically an alteration product. It may be accompanied by a variety of sulphides (pyrite, sphalerite, galena), Fe-Mn-Mg-Ca carbonates, chlorite, barite, gypsum or anhydrite and fluorspar. High temperature/low pressure metamorphism may result in converting dolomite into a mixture of periclase (Mg0) and calcite. Periclase in nature easily alters into brucite Mg(OH)2.

 

 

WEATHERING:  In outcrop dolomitic layers in limestone may have a positive relief because of their lower solubility. Common to see concentrations of iron in the rims of individual dolomite crystals which result in the brown-yellow colour of dolomite outcrops. Because of higher porosity, some secondary dolomites are more susceptible to physical weathering and outcrops have frequently sandy talus developments (because of the sugary texture).

 

ORE CONTROLS:  Ore control reflects the mode and intensity of dolomitization. In some deposits a primary control is the chemical composition of the carbonate rock, in some others it is the upper and lower limits of the original limestone bed. For some deposits, the locations where fluid pathways along faults and permeable zones intersect reactive carbonate rocks are the control on the location of the replacement zones.


GENETIC MODEL:  

A number of models for dolomitization have been suggested by the scientific community.

·         Hypersaline water from a shelf lagoon percolated through the underlying sediment, transforming calcium carbonate into dolomite.

·         Burial compaction resulting in expulsion of pore water containing Mg2+ from shales may react with

adjacent limestones to form dolomite.

·         Elevated topography of a mountain thrust belt provides the hydrodynamic potential for gravity-driven meteoric fluids which became enriched in soluble components, including Mg2+, that react

with calcium carbonate beds in the subsurface to form stratiform dolomite zones.

·         Tectonic loading and compression during the buildup of orogenic thrust belts may cause the rapid
expulsion of formation fluids into the foreland basins and bring the necessary Mg2+ to react with

limestone deposits in the basin.

The two models listed below are currently the most popular explanation for most of global dolomites.

·         Dolomitization can occur within the mixing zone of phreatic sea water with fresh groundwater. The Mg2+ ions for dolomitization are derived primarily from seawater. The delivery mechanism is the

continual circulation of seawater induced by the flow of fresh groundwater.

·         Deep convection circulation of basinal brines has been invoked for forming some regional subsurface dolomites. Deep crustal scale convection of meteoric ground waters to 10 kilometres depth appears to have been the dominant subsurface flow during Early Tertiary time in southeastern B.C. Thermal convection can support long-lived flow systems that are capable of cycling subsurface solutions many times through the rock mass. Alternately thermal convection can occur in strata beneath the sea bed, the sea water-derived solutions would be continuously added to the system to provide an ongoing source of magnesium.

 

ASSOCIATED DEPOSIT TYPES:  Mississippi Valley Type Pb, Zn (E12), barite (E17) and fluorspar (E11) deposits, limestone (R09), accumulations of oil and natural gas, hydrogen sulphide.

 

COMMENTS:  Most dolomite production is as quarried rock for use as aggregate which relies mainly on its physical properties.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATUREHigh magnesium in carbonate rock.

 

GEOPHYSICAL SIGNATUREWhile karst features in dolomite are rather uncommon, resistivity and gravity could be used to outline karst affected areas.


OTHER EXPLORATION GUIDES:  Sometimes yellow or brown colour of outcrops, sandy talus. Because of lower solubility, dolomite does not fizz with diluted hydrochloric acid.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  Commercial dolomite must be very high purity carbonate rock, and almost stochiometric in composition (30.4% CaO and 21.9% MgO). Industry specifications are set for the calcined product – i.e. a dolomitic lime. Depending on the end use, the limits for impurities are usually between 0.1 and 4.5 % Fe2O3, SiO2 between 0.5 and 1.0%, and Al2O3 between 0.3 and 0.8%.

 

ECONOMIC LIMITATIONS:  Information on dolomite production is difficult to obtain. In mineral statistic data, dolomite is covered together with limestone, and individual uses are frequently confidential. It is estimated, that USA and Canada together produce 500,000 tonnes of calcined dolomite annually. The quantity of dolomite used as a granular or ground industrial product is  not relatively small. Dolomite used for magnesium metal may be as much as one million tonnes annually, but is gradually being replaced by other sources, such as seawater. Some limestone operators produce dolomite and limestone from different beds as coproducts.

 

END USES:  Refractory products, magnesium metal ore, dolomitic lime, glass, desulphurization of coal, iron and steel, smelter flux, variety of fillers, mineral wool, agriculture soil conditioner. 

 

IMPORTANCE: As a source of magnesium to improve a fluidity of molten product, like in mineral wool. float glass, slag in metallurgical process very important. As agriculture soil conditioner the magnesium content improves the neutralizing power, and helps to retain the soil nutrients better than pure limestone. In many other end uses dolomite can be substituted by some other industrial minerals.

 

REFERENCES

 

Anani, A. (1984): Applications of Dolomites. Industrial Minerals, Number 205, pages 45-55.

Bathurst, R.G.C. (1975): Carbonate Sediments and their Diagenesis, Elsevier Scientific Publishing Company, 658 pages.

Bowles, O. (1956): Limestone and Dolomite, U.S. Bureau of Mines, IC 7738, 29 pages.

Carr, D.D., Rooney, L.F. and Freas, R.C. (1994): Limestone and Dolomite, on Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages 605-629.

Cervato, C. (1990): Hydrothermal Dolomitization of Jurassic-Cretaceous Limestones in the Southern Alps (Italy): Relation to Tectonics and Volcanism, Geology, v.18, pages 458-461.

Colby, S.F. (1941): Occurrences and Uses of Dolomite in the United States, U.S. Bureau of Mines, IC 7192, 21 pages.

Fischl, P. (1992): Limestone and Dolomite Resources in British Columbia Ministry of Energy, Mines and Petroleum Resources, Open File 1992 – 18, 150 pages.

Goudge, M.F. (1934): Limestones of Canada. Part II Maritime Provinces, Canada Department of Mines, No.742, 186 pages.

Goudge, M.F. (1935): Limestones of Canada. Part III Quebec, Canada Department of Mines, No. 755, 274 pages.

Goudge, M.F. (1938): Limestones of Canada. Part IV Ontario, Canada Department of Mines, No. 781, 362 pages.

Goudge, M.F. (1944): Limestones of Canada, Part V Western Canada, Canada Department of Mines, No.811, 233 pages.

Hopkins, D.A. (1985): Refractory Dolomite Production in a Geologically Complex Area, in Glaser, J.D. and Edwards, J., Editors, Proceedings, Twentieth Forum on the Geology of Industrial Minerals, Maryland Geological Survey, Special Publication No.2, pages 117-124.

Machel, H.G. (1987): Saddle Dolomite as a By-Product of Chemical Compaction and Thermochemical Sulfate Reduction, Geology, Volume 15, pages 936-940.

Machel, H.G. (2005): Investigations of Burial Diagenesis in Carbonate Hydrocarbon Reservoir Rocks, Geoscience Canada, Volume 32, pages 103-128.

Morrow, D. (1982): Diagenesis 1. Dolomite – Part 1: The Chemistry of Dolomitization and Dolomite Precipitation, Geoscience Canada, Volume 9, Number 1, pages 5-13.

Morrow, D. (1982): Diagenesis 2. Dolomite – Part 2 Dolomitization Models and Ancient Dolostones, Geoscience Canada, Volume 9, Number 2, pages 95-107.

Morrow, D. (1998): Regional Subsurface Dolomitization: Models and Constraints, Geoscience Canada, Volume 25, Number 2, pages 57-70.

Nelson, J.A., Paradis, S., Christensen, J. and Gabites, J. (2002): Canadian Cordilleran Mississippi Valley-Type Deposits: A Case for Devonian-Mississippian Back-Arc Hydrothermal Origin, Economic Geology, Volume 97, pages 1013-1036.

Nesbitt, B.E. and Muehlenbachs, K. (1994): Paleohydrogeology of the Canadian Rockies and Origins of Brines, Pb-Zn deposits and Dolomitization in the Western Canada Sedimentary Basin, Geology, Volume 22, pages 243-246.

O`Driscoll, M. (1988): Dolomite - More than Crushed Stone, Industrial Minerals, Number 252, pages 37-63.

Qing, H. and Mountjoy, E. (1992): Large-scale Fluid Flow in the Middle Devonian Presqu`ile Barrier, Western Canada Sedimentary Basin, Geology, Volume 20, pages 903-906.

Simandl, G.J., Paradis, S. and Irvine, M. (2007): Brucite – Industrial Mineral With a Future, Geoscience Canada, Volume 34, Number 2, pages 57-64.

Smith, A. (1983): Dolomite – Steel Upturn Casts Ray of Hope, Industrial Minerals, Number 190, pages 21-40.

Weitz, J.H. (1942): High-Grade Dolomite Deposits of the United States, U.S. Bureau of Mines, IC 7226, 86 pages.

 

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Volcanic Ash/Cinder and Pumice

R11
by Z.D. Hora

Retired, British Columbia Geological Survey, Victoria, B.C., Canada

IDENTIFICATION

 

SYNONYMS: Volcanic scoria, volcanic ejecta, agglomerate, pyroclastics, lapilli, tuff.

 

COMMODITIES (BYPRODUCTS): Lightweight aggregate, landscaping aggregate, anti-skid sand, stonewashing pumice, "lava (barbecue) rock", pozzolan, abrasive powders, absorbents, insulation fill, filler, filtration media.

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  PUMICE - Mt. Meager (092JW040), Salal Creek (092JW039), Mt. Meager, Bridge River ash, Nazco (093G1/4), Wells Grey Park; Bend (Oregon), Mono Crater, San Bernardino (California), Flagstaff (Arizona), Grant, Albuquerque (New Mexico), Lipari (Italy), Thyra (Greece), Haparangi, Waitahanaui, Mihi (New Zealand). CINDER – Nazco (093G/4), Wells Grey Park, Flagstaff (Arizona),Grant, Albuquerque (New Mexico), San Bernardino (California).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  Unconsolidated pumice, cinder and other pyroclastic deposits are usually found near a volcanic vent or edifice. It is typically the vesicular pyroclastic material that is exploited because of its appearance or attractive strength to weight ratio. Pumice occurs in felsic pyroclastic flows, air-fall blankets and flow domes; cinder usually forms basaltic pyroclastic tephra cones and blankets.

TECTONIC SETTINGS: Volcanic arcs and rift zone belts.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Pumice in calderas, lava flow dome complexes and Plinian-type central eruptions. Blanket deposits are found in the vicinity of stratovolcanoes.

 

AGE OF ROCK FORMATION: Any age, although preserved deposits are commonly Tertiary to recent. In Canada, older deposits are commonly eroded by glaciation.

 

HOST/ASSOCIATED ROCK TYPES: Ash, lapilli and agglomerate pyroclastic deposits. Associated with lava flows, high-level dikes, ash flows and flow domes. All these rock types can vary in composition from rhyolite to basalt.

 

DEPOSIT FORM: Cinder cones can be elliptical or circular in plan view, or elongated in the case of a fissure vent. Individual cones can be up to hundreds of metres high and more than a kilometre in diameter. The largest cinder cone in USA and Canada, located near Flagstaff, Arizona, is 1 kilometre in diameter and 200 metres in height. Larger cinder cones may be seen in active volcanic regions. Airfall ejecta form blankets composed of multiple units that can be 5 to 13 metres thick (Bend, Oregon). The Mazama ash covers area of 5 200 square kilometres with thicknesses of 1 to 3 metres.

 

TEXTURE/STRUCTURE: Clinker-like, rough, irregular fragments of lava thrown out by explosive eruption. Pumice and cinder are composed of vesicular, volcanic glass that may contain minor phenocrysts of feldspar, various forms of quartz, mica and/or a number of ferromagnesian minerals. Pyroclastic flows, flow domes and sometimes cinder cones consist of unsorted particle sizes. Air-fall blankets are usually sorted with particle size decreasing with distance from the eruption centre and intensity of the eruption.

 

ORE: Pumice, cinder, volcanic ash, bombs, blocks.

 

GANGUE [Principal and subordinate]: Waste consists of altered, fractured and unsound rock; stone containing inhomogenities, like blacks knots and aggregates of mafic minerals; and any minerals that  upon weathering could produce stains, e.g. pyrite, chalcopyrite.

ALTERATION MINERALOGY: Clay minerals, alunite, zeolites, hematite, limonite.

 

WEATHERING: Weathered pyroclastics may deteriorate physically into smaller, dust-sized particles and chemically into palagonite, clay minerals, limonite, jarosite and alunite. In both cases, this can reduce the value of the material significantly.

 

ORE CONTROLS: Pumice, a product of highly viscous rhyolite magma, commonly forms an ash-fall blanket surrounding the source vent. Its thickness depends on intensity and longevity of eruption. Large volumes of pumice and pumiceous rhyolite also accumulate in the upper parts of rhyolite and obsidian flow domes, as well in ash-flow tuffs in calderas. Volcanic cinder, because of low viscosity and higher density of the mafic magma, is more concentrated in proximity to the vent as cone-shaped deposits.

GENETIC MODEL: The formation of highly vesicular rocks involves the interplay of temperature, viscosity, gas pressure and gas diffusion rates within the erupting magma, and external conditions, such as wallrock permeability, water influx and vent blockage. Conditions that reduce gas escape may lead to violent eruptions, during which the suddenly released pressure results in the expansion of volatiles in frothy masses of expelled lava. These cool quickly in the atmosphere to form glass fragments with innumerable bubble cavities. Basaltic magmas tend to be relatively fluid, allowing more gases to escape and producing less vesicular ejecta (cinder). Silicic magmas are more viscous and offer less opportunity for gas to escape. Therefore, pumice can be extremely vesicular and can float in water. In rhyolite flow domes, pumiceous rhyolite flow breccias are associated with perlite or obsidian flows and felsic dikes.

 

ASSOCIATED DEPOSIT TYPES: Perlite (R12), open and closed system zeolites (D01, D02), andesite dimension stone (R05). Secondary deposits are produced by erosion of primary deposits and subsequent deposition in stream and river beds, for example, in Kansas and Oklahoma, USA, or along the Waikato and Wanganui Rivers in New Zealand.

 

COMMENTS: Free silica is a potential health hazard in rhyolite pumice, and dusty material must be handled accordingly. Natural clinker, rocks heated by burning underground coal seams, can be used as an alternative to volcanic cinder.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: For pumice, look for rhyolite compositions.

 

GEOPHYSICAL SIGNATURE: Ground penetrating radar can delineate structure and thickness of a pyroclastic deposit. Shallow seismic surveys can help to outline the presence of lave flows or dikes in cinder cones, as well as the boundary between pumiceous rhyolite and non-porous rock facies.

OTHER EXPLORATION GUIDES: Proximity to volcanic vents, particularly on the downwind side; areas with remnant volcanic edifices. Remote sensing and air photo interpretation are useful to map the limits of cinder and pumice blanket areas.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Deposits range in size from 10 000 to 10 million tonnes, although occasionally, deposits may reach 400 million tonnes in size. The average production from a single deposit in western USA is approximately 35 000 tonnes per year for cinder and 10 000 tonnes per year for pumice. Use of a lightweight aggregate has several ASTM specifications for particle sizing and unit weight. So do some specific end uses, like stone washing, for example.

 

ECONOMIC LIMITATIONS: Lightweight aggregate transportation costs ultimately determine the geographic extent of the market as it can be substituted by expanded shales and similar products. Only specialty products, like ‘barbecue lava rock’, stone washing pumice, absorbents, landscaping cinder and filter media can reach more distant markets. The demand for these specialty products is only a fraction of total production.

 

END USES: The main use for pumice is as lightweight aggregate in concrete and masonry, with smaller quantities consumed for in horticulture, stone washing, abrasives and filter media, and pozzolan. Volcanic cinder is also used as lightweight aggregate, in landscaping, as road and highway aggregate and for skid control on icy highways.

 

IMPORTANCE: Regionally important as a specialty aggregate, but represents only a small portion of the overall aggregate market in North America (0.1% in the year 2000).

 

SELECTED BIBLIOGRAPHY

 

Bolen, W.P. (2001): Pumice and Pumicite; in Mineral Industry Surveys, U.S. Geological Survey, pages 60.1–60.7.

Bryan, D. (1987): Natural Lightweight Aggregates of the Southwest; in Proceedings of the 21st Forum on the Geology of Industrial Minerals, Pierce, H.W., Editor, Arizona Bureau of Geology and Mineral Technology, Special Paper 4, pages 55-63.

Geitgey, R.P. (1994): Pumice and Volcanic Cinder; in Industrial Minerals and Rocks, Carr, D.D., Senior Editor, Society for Mining, Metallurgy and Exploration, Inc., Littleton, Colorado, pages 803-813.

Harben, P.W. and Bates, R.L. (1990): Industrial Minerals. Geology and World Deposits, Metal Bulletin Plc, London, U.K., 312 pages.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals. A Global Geology, Metal Bulletin Plc, London, U.K., 46 pages.

Hora, Z.D. and Hancock, K.D. (1995): Nazco Cinder Cone and a New Perlite Occurrence, BC Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, pages 405-410.

Osburn, J-A.C. (1982): Scoria Exploration and Utilization in New Mexico; in Austin, G.S., Editor, Industrial Rocks and Minerals of the Southwest, New Mexico Bureau of Mines and Mineral Resources, Circular 182, pages 57-59.

Read, P.B. (1990): Mount Meager Complex, Garibaldi Belt, Southwestern British Columbia. Geoscience Canada, Volume 17, pages 167-170.

Sutherland Brown, A. (1969): Aiyansh Lava Flow, British Columbia, Canadian Journal of Earth Sciences, Volume 6, Number 6, pages 1460– 1468.

Thompson, B., Brathwaite, B. and Christie, T. (1995): Pumice; in Mineral Wealth of New Zealand; Institute of Geological & Nuclear Sciences Limited, Information Series 33, pages 135-136.

Wilkerson, G. and Hoffer, J. (1995): Pumice for Stone-washed and Acid-washed Textiles: Benton Pumice Beds, Mono County, California; in Tabilio M. and Dupras D.L., Editors, 29th Forum on the Geology of Industrial Minerals: Proceedings, California Department of Conservation, Special Publication 110, pages 119–122.

Perlite

R12
by Z.D. Hora

Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Onion skin rhyolitic glass, pitchstone, obsidian.

 

COMMODITIES (BYPRODUCTS): Expanding perlite (pumice, foundry flux, synthetic zeolite feedstock)

 

EXAMPLES (British Columbia (MINFILE) - Canada/International): Frenier (092O 072), Francois Lake (093K 001), Uncha Lake (093F 026), Mount Tuzo (Quebec), No Agua, Grants, Socorro (New Mexico, USA), Caliente (Nevada, USA), Malad City (Idaho, USA), Greece, Italy, Turkey.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Hydrated volcanic glass, usually of rhyolite composition, formed through secondary alteration by the incorporation of water into the glass/silica structure. It is often distinguished by vitreous, pearly luster and concentric (onion skin) fractures. When heated, it will expand up to ten to forty times its original volume.

 

TECTONIC SETTINGS: Orogenic rift belts and volcanic arcs.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Rapidly cooled volcanic rocks of rhyolite composition occurring as the glassy parts of domes and flows, vitric tephra, chill margins of dikes and sills, and welded ash-flow tuffs.

 

AGE OF MINERALIZATION: Normally Tertiary through middle Quaternary, occasionally older.

 

HOST/ASSOCIATED ROCK TYPES: Perlite is hosted by flow domes and lava flows of rhyolite composition. Most obsidian contains less than 1% of total water (water left after heating to 105°C), the hydration of perlite increases the water content level to 2 to 5%, but may reach as much as 10%. It is associated with vitric tephra, ash-flow tuffs, pumiceous rhyolite and pumicite.

 

DEPOSIT FORM: Perlite deposits are very irregular in shape, reflecting the original extent of the glassy volcanic rock and the zones that have experienced significant hydration. The boundaries are usually gradational from perlite to obsidian to devitrified volcanic glass to a crystalline felsite core. Perlite deposits are usually measured in hundreds of metres in horizontal dimensions and metres to tens of metres in the vertical dimension. Big Pine deposit in California has a perlite thickness of 27 metres; Picketpost Mountain in Arizona is 2 to 17 metres thick. The No Agua Peaks deposit in New Mexico is considered the largest in North America and is 50 metres thick, covering 10 square kilometres. The Socorro perlite deposit in New Mexico is 200 metres thick and covers an area of 0.7 square kilometres.

 

TEXTURE/STRUCTURE: Many flows and domes are texturally zoned, reflecting the rapid cooling of exterior surfaces and slower crystallization within the interior. The glass mantle can occur at the base, margin, and/or near the top of the flow. Hydration and resulting perlitic cracks due to expansion by the incorporation of water are superimposed on primary textures of flow. Perlite can have classical, concentric, and arcuate onion skin-like fractures with remnant obsidian kernels; a granular texture with obsidian remnants absent; or a pumiceous and vesicular character.

 

ORE: Expandable hydrated siliceous volcanic glass. Most commercial perlites are ‘high silica rhyolites’ with 75 to 77.5% of SiO2. In a few countries, obsidian and pitchstone are also expanded.

 

GANGUE MINERALOGY (Principal and subordinate): Non-hydrated obsidian, devitrified glass, microlites or small phenocrysts of feldspar, mica and quartz; sometimes with chalcedony and clay fracture filling.

 

ALTERATION MINERALOGY: Since volcanic glass is unstable, devitrification changes Tertiary age or older volcanic glass into a microcrystalline equivalent (there may be some rare exceptions of older volcanic glass being preserved). Hydrothermal alteration can introduce clay minerals and/or chalcedony and can produce deposits of halloysite.

 

WEATHERING: Because of high fracture density, exposed perlite is highly susceptible to both physical and chemical weathering. Chemical weathering can be very fast in humid and temperate climate conditions. Weathering products such as palagonite, clay minerals and calcium carbonate are commonly present as infilling of cracks and fissures. Excessive fines and clay presence may render the perlite deposit uneconomic.

 

ORE CONTROLS: Perlite forms carapaces that partially or fully comprise extrusive domes and flows, tephra and tuff beds, where percolating meteoric water had access to hydrate the glassy volcanic material. Since felsic flows are viscous, most perlite deposits from proximal to the volcanic vent.

 

GENETIC MODEL: Glassy component of rhyolite volcanic rocks wherever accessible to percolating meteoric water, mostly on top, but sometimes also at the bottom of the dome flow. Hydration of obsidian and the formation of perlite is a gradual process, coincident with the inward migration of meteoric water into glass selvages and its incorporation into glass structure as molecular water. Hydration rate slows with decreasing temperature and with increasing calcium and magnesium content in the glass. The rate increases with increasing silica content.

 

ASSOCIATED DEPOSIT TYPES: Pumice, pumiceous rhyolite (R11).

 

COMMENTS: Petrological definition of perlite covers all glass with perlitic texture, including the non-expanding varieties. The presence of crystalline silica is considered as a potential health hazard, and the product has to be controlled and handled accordingly. Some perlites are sensitive to decrepitation. This can be controlled by preheating and by adjusting the temperature regime during the expansion process.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: Felsic volcanics with more than 65% silica, preferably greater, up to 75%; water contents of 2 to 10%.

 

GEOPHYSICAL SIGNATURE: Hydrated glass can be distinguished from non-hydrated obsidian by electrical properties.

 

OTHER EXPLORATION GUIDES: A small portable blow torch is the most effective field test. A potential perlite either expands or decrepitates; non-expanding rock just glows red. Detailed mapping must delineate rock types, perlite textures and the abundance of contaminants, such as clay, felsite, phenocrysts and obsidian. A great variability of textures and zonation require careful deposit modeling. For drilling the potential deposit, the core diameter must be large enough to ensure high and representative core recovery.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Average perlite has an expanded density between 20 and 40 kg per cubic metre. Some deposits can contain up to 15% non-perlite material. The quality of perlite products is controlled by performance standards developed by the Perlite Institute, as well as ASTM specifications. Deposits range in size from less than 5 Mt to more than 100 Mt. The Frenier deposit produced 6000 tonnes over 3 years from an inferred reserve of 3.8 Mt. In New Zealand, the Maungaiti dome, and at Awana, on Great Barrier Island, there are 20 Mt and 100 Mt of inferred resources respectively. Annual production in North America is reported between 500 000 and 600 000 tonnes annually. It comes from 10 production centres in western USA.

 

ECONOMIC LIMITATIONS: Perlite is usually mined from open pits (the Caliente deposit in Nevada is underground) and processed in expanding plants located in market areas. Raw perlite is shipped by truck, or by rail and boat to more distant processing plants. The average capacity of an expanding plant is about 10 000 tonnes per year. As a relatively large volume product, perlite products are sensitive to transportation costs.

 

END USES: Crushed perlite is heated to between 900 and 1200°C to create steam in the molten rock that produces gas bubbles. The product is cooled to form globules of artificial pumice. The light, fluffy globules are known commercially as ‘perlite’ and marketed with different brand names. They have a porous texture with low density and thermal conductivity and high sound absorption and chemical stability. Construction uses, such as insulation products and acoustic tile, accounted for 66% of North American consumption in the late 1990s. Horticulture and a variety of fillers accounted for 19%, and filter aid products make up the remaining 15%.

 

IMPORTANCE: Important for horticulture and for construction products. Expanded perlite has a very limited number of substitutes; therefore, it can be shipped considerable distances. For example, Greece has exported perlite to the eastern seaboard of North America, while New Mexico supplies Canada and numerous eastern US locations.

 

SELECTED BIBLIOGRAPHY

 

Austin, G.S. and Barker, J.M. (1994): Production and Marketing of Perlite in the Western United States; in Tabilio. M. and Dupras, D.L., Editors, 29th Forum on the Geology of Industrial Minerals: Proceedings, California Department of Conservation, Special Publication 110, pages 39-68.

Barker, J.M., Chamberlin, R.M., Austin, G.S. and Jenkins, D.A. (1996): Economic Geology of Perlite in New Mexico; in Hoffman, G. K., Barker, J. M., Zidek, J., and Gilson, N. [Editors], Proceedings of the 31st Forum on the Geology of Industrial Minerals-The Borderland Forum, New Mexico Institute of Mining and Technology, Bulletin 154, pages 165–170.

Barker, J.M. and Bodycomb, F. (1996): Perlite Markets: Expanding … Or Not?; in notes for Industrial Minerals '96, conference in Toronto organized by Blendon Information Services, October,19 pages.

Bolen, W.P. (2001): Perlite; in Mineral Industry Surveys, U.S. Geological Survey, pages 56.1–56.7.

Chamberlin, R.M. and Barker, J.M. (1996): Genetic Aspects of Commercial Perlite Deposits in New Mexico; in Austin G.S., Hoffman, G.K., Barker, J.M., Zidek J. and Gilson, N., [Editors], Proceedings of the 31st Forum on the Geology of Industrial Minerals – The Borderland Forum, New Mexico Institute of Mining and Technology, Bulletin 154, pages 171–186.

Gunning, D.F. and McNeal & Associates Consultants Ltd. (1994): Perlite Market Study; BC Ministry of Energy, Mines and Petroleum Resources, Open File 1994-21, 44 pages.

Friedman, I., Smith, R.L. and Long, W.D. (1966): Hydration of Natural Glass and Formation of Perlite, Geological Society of America, Bulletin, Volume 77, pages 323–328.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals. A Global Geology, Metal Bulletin PLC, London, UK, 462 pages.

Rotella, M. and Simandl, G.J. (2003): Marilla Perlite – Volcanic Glass Occurrence, British Columbia; in Geological Fieldwork 2002, B.C. Ministry of Energy and Mines, Paper 2003-1, pages 165–174.

Thompson, B., Brathwaite, B. and Christie, T. (1995): Pumice; in Mineral Wealth of New Zealand; Institute of Geological & Nuclear Sciences Limited, Information Series 33, page 133.

White, G.V. (2001): Perlite in British Columbia; in Dunlop, S. and Simandl, G., Editors, Industrial Minerals in Canada, Canadian Institute of Mining, Metallurgy and Petroleum, Special Volume 53, pages 59–65.

Whitson, D.N. (1982): Geology of the Perlite Deposit at No Agua Peaks, New Mexico; in Austin, G.S., Editor, Industrial Rocks and Minerals of the Southwest, New Mexico Bureau of Mines & Mineral Resources, Circular 182, pages 89–96.

 

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Nepheline Syenite

R13
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Undersaturated granitoids.

 

COMMODITIES (BYPRODUCTS): Nepheline syenite (magnetite, apatite).
 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  

·         Sodium Feldspar-rich: Trident Mountain (082M173), Mount Copeland (082M002);
Blue Mountain, (Ontario), Fourche Mountain, Arkansas, Wind Mountain, New Mexico, Stjernoy Island, Norway, Khibina Massif, Russia.

·         Potassium Feldspar-rich: No producers yet. Kruger Mountain (082ESW106), Barriere (092P 159).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONSodium Feldspar Rich: Small alkalic intrusive bodies of white, granular feldspathic rocks composed essentially of soda and potash feldspars and nepheline, with accessory biotite, hornblende, magnetite, apatite, sodalite and cancrinite.

 

TECTONIC SETTINGSNepheline syenites are found in continental settings and at convergent plate boundaries.

·         Sodium Feldspar-rich: Continental environment generally associated with extensional faulting and major rift zones and grabens that can control extensive alkaline igneous provinces. Economic deposits of nepheline and apatite are associated with this setting.

·         Potassium Feldspar-rich: In orogenic belts, commonly oceanic volcanic island arcs overlying oceanic crust. Magmatism with alkalic composition varies from gabbro to nepheline syenite. The magmas are introduced inboard parallel to the axis of the arc that coincides with deep-seated faults.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING:  

·         Sodium Feldspar-rich: Intrusive bodies and plugs, differentiated ring complexes frequently associated with carbonatites; sills, dikes and layered intrusives that intrude Precambrian to Mesozoic continental clastic and carbonate rocks. Many known ages predate major regional unconformities and may be manifestations of crustal upwelling and extension.

·         Potassium Feldspar-rich: High level stock emplacement levels in magmatic arcs. The high level stocks and related dikes intrude their coeval and cogenetic volcanic equivalents.


AGE OF MINERALIZATION:  

·         Sodium Feldspar-rich: Mid-Proterozoic to Eocene. Recent volcanoes along the Kenya Rift.

·         Potassium Feldspar-rich: Archean to Cretaceous, in Canadian Cordillera mostly Late Triassic to Early Jurassic.


HOST/ASSOCIATED ROCK TYPES:  

·         Sodium Feldspar-rich: A broad spectrum of sedimentary rocks and their metamorphic equivalents / carbonatite complexes with a variety of nepheline containing intrusive rocks, fenites.

·         Potassium Feldspar-rich: Multiple emplacement of successive intrusive phases with composition from alkalic gabbro to syenite. The most undersaturated nepheline normative rocks commonly contain pseudoleucite. Volcanic equivalents are mostly basic in composition and only rarely phonolite.


DEPOSIT FORMSodium Feldspar-rich:  Intrusive bodies in a variety of shapes, including dikes, sills, stocks and small plutons and layered complexes. Two production centres in Ontario are mining 200 to 300 metre wide zones of biotite/magnetite/muscovite facies of a nepheline syenite intrusion. The intrusion is 1 by 4 kilometres at surface; with a 400 metre wide apophysis extending 6 kilometres to the southwest. In Norway, an underground mine is exploiting a hornblende/pyroxene facies of nepheline syenite, which forms about 80% of lenticular body 1800 metres long and up to 300 metres wide.

 

TEXTURE/STRUCTURE:  A typical nepheline syenite ore deposit is a relatively uniform rock consisting of albite, microcline, nepheline and a few percent of mafic minerals, namely magnetite, biotite and hornblende. The rock is typically white, medium grained, with an open granitic texture. The rock mined in Norway is well foliated. For commercial use in glass and ceramics the mafic minerals must be coarse grained enough to allow for separation at about 20 mesh. Under the microscope, the texture may suggest a metasomatic process had a role in the rock`s composition.


ORE MINERALOGY [Principal and subordinate]:  

·         Sodium Feldspar-rich: Albite, microcline and nepheline, often apatite, magnetite; cancrinite, sodalite, calcite. In some nepheline syenites, apatite with zirconium and titanium minerals can attain rock-forming proportions.

·         Potassium Feldspar-rich: Magnetite and apatite may form high grade accumulations of economic interest.


GANGUE MINERALOGY [Principal and subordinate]:  

·         Sodium Feldspar–rich: Magnetite, biotite, hornblende; zircon, corundum, pyroxene, sphene, apatite.

·         Potassium Feldspar-rich: Pyrite in apatite/magnetite deposits.

 


WEATHERING: The weathered surface varies from a dove-grey to distinctly bluish colour.  This and the pitted surface are the most distinctive characteristics for recognition in the field.  Intense lateritic weathering of nepheline syenite may produce economic deposits of bauxite (for example, Pocos de Caldas, Brazil).  

 

ORE CONTROLS: Nepheline syenite occurs as alkalic intrusions with strong structural control.  Specific phases in albite-rich nepheline syenites can be ore if they are easy to process into a low iron commercial product free of detrimental minerals like corundum.

 
GENETIC MODELSNepheline syenite occurs as undersaturated, alkali – rich leucocratic magma intrusive bodies with a metasomatic alkali overprint. They are generally small, discordant intrusions, with few signs of forceful emplacement. Simple stoping and emplacement along ring fractures and as a consequence of cauldron subsidence have all been proposed as intrusion mechanisms. Common mafic minerals are mica, amphibole and pyroxene. The contacts between intrusive phases is transitional in both Blue Mountain and Stjernoy Island deposits. In the Khibina massif complex intrusion, the sequence of rock units from oldest to youngest developed from peridotite to pyroxenite to potassium-rich nepheline syenite to nephelinite to carbonatite. An apatite-rich unit is part of the potassium-rich nepheline syenite phase. Syenite gneiss complexes are likely the metamorphosed and deformed equivalents of original nepheline syenites intrusions. Some have been interpreted as possible products of fenitization and metasomatism.

 
ASSOCIATED DEPOSIT TYPESApatite-rich phase in ultramafic complexes, carbonatite hosted deposits (N01).

 
COMMENTSThe former USSR developed an aluminum industry based on processing  originally wasted nepheline produced in large volumes from apatite mining that has operated since 1941. This industry was developed for strategic reasons because of the lack of domestic bauxite deposits. Phonolite is a  fine grained volcanic equivalent of nepheline syenite. Leucocratic varieties of phonolite are used in some countries in place of nepheline syenite for making coloured types of container glass.  


EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURESodium Feldspar-Rich type is more sodium rich, while the Potassium Feldspar-Rich type is more potassic.

 

GEOPHYSICAL SIGNATURE:  Magnetic and IP surveys can distinguish between nepheline syenite intrusions and many types of surrounding rocks.

 

OTHER EXPLORATION GUIDES:  Explore for nepheline syenite intrusions that are generally small and elongate in shape.  In complex intrustions the later phases seem to be more likely to have lower iron contents and be more nepheline-rich.  Detailed geological mapping and petrographical study can assist with identifying attractive intrusive phases. Uniformity, grain size which will allow to separate mafic minerals from a commercial product, absence of refractory minerals. White colour is desirable for filler applications. 

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE:  Deposits can be volumetrically very large, although often only a portion can be mined at a profit.  Typical nepheline syenite produced from the Blue Mountain deposit in Ontario has 60.2% SiO2, 23.5% Al2O3, 0.08% Fe2O3, 10.6% Na2O and 5.1% K2O. The higher the nepheline content the better. The annual

 

output in Canada is between 500,000 and 600,000 tonnes from two production centers in Ontario. Only sodium feldspar-rich are of economic interest.


ECONOMIC LIMITATIONS: As a typical bulk and low cost product, nepheline syenite is not usually shipped very far.  Canadian deposits are mined as open pits while the deposit in Norway is mined by underground methods because it has suitable morphology and it minimizes the impact of severe winters.  For nepheline syenite to be an economic resource it must be reasonably uniform, light coloured, medium to coarse grained with minimal mafic mineral intergrowths.  The rock should be, rather massive or only moderately gneissic.  The absence of refractory minerals, like corundum or zircon, is a must for glass grade product. 

 

IMPORTANCENepheline syenite is the preferred source of alumina and alkalies for glass manufacturing. In some countries with phonolite resources, the nepheline syenite volcanic equivalent is used for coloured glass in spite of a much higher iron content. In markets more distant from nepheline syenite sources, a feldspar resource (alaskite, aplite, leucocratic granitoids, feldspathic sands) is used instead. Glass recycling is increasingly important secondary source of a raw material for new glass products. Blast furnace slag and “calumite” (artificial slag prepared as glass raw material) are also used in some types of glass products.

 

 

REFERENCES

  

 

Andrews, P. (1992): Nepheline Syenite; in Canadian Minerals Yearbook, Minerals and metals Sector, Natural Resources Canada, pages 34.1 – 34.5.

Bolger, R.B. (1995): Feldspar and Nepheline Syenite; Industrial Minerals, Number 332, May, pages 25-45.

Currie, K.L. (1976): The Alkaline Rocks of Canada,Geological Survey of Canada, Memoir 239, 228 pages.

Duke, N.A. and Edgar, A.D. (1977): Petrology of the Blue Mountain and Bigwood Felsic Alkaline Complexes of the Grenville Province of Ontario; Canadian Journal of Earth Sciences, volume14, Number 4, pages 515-538.

Geis, H.P. (1979): Nepheline Syenite on Stjernoy, Northern Norway; Economic Geology, Volume 74, pages 1286 – 1295.

Guillet, G.R. (1994): Nepheline Syenite; in Carr, D.D., Senior editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, pages  711-730.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals. A Global Geology; Metal Bulletin PLC., London, UK, 462 pages.

McLemore, V.T. (2006): Nepheline Syenite; in Kogel, J.E., Trivedi, N.C., Barket, J.M. and Krukowski, S.T., editors, Industrial Minerals and Rocks,Commodities, Markets and Uses,Society for Mining, Metallurgy and Exploration, Inc.,Lttleton, Colorado, pages 653 – 670.

McVey, Hal (1988): A Study of Markets for British Columbia`s Nepheline Syenite and Feldspathic Minerals; Unpublished report, B.C. Ministry of Energy, Mines and Petroleum Resources, 91 pages.

Mitchell, R.H., Editor (1996): Undersaturated Alkaline Rocks: Mineralogy, Petrogenesis, and Economic Potential; Mineralogical Association of Canada, Short Course Volume 24, 312 pages.

Pell, J. (1994): Carbonatites, Nepheline Syenites, Kimberlites and Related Rocks in British Columbia;B.C. Ministry of Energy,Mines and Petroleum Resources,Bulletin 88, 135 pages.

Potter, M.J. (2001): Feldspar and Nepheline Syenite; in Mineral Industry Surveys, U.S. Geological Survey, pages 26.1-26.7.

Turek, V. and MacGregor, D. (1984): Blue Mountain Nepheline Syenite Deposit, Nephton, Ontario; in Guillet, G.R. and Martin,W., The Geology of Industrial Minerals in Canada, Canadian Institute of Mining and Metallurgy, Special Volume 29, pages 125 – 128.

 

 

 

Feldspar-rich Rocks (Alaskite)

R14
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Feldspar, sodaspar, feldspar ore, feldspar rock, leucosyenite.

 

COMMODITIES (BYPRODUCTS/COPRODUCTS): Feldspar (silica, mica).
 

EXAMPLES (British Columbia (MINFILE #) - Canada/International):  

Boundary Creek (082ESE224), Sumas Mountain (092GSE037), Spruce Pine, North Carolina, Monticello, Georgia, Montpelier, Virginia, Middletown, Connecticut.

 

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTIONFeldspathic igneous rocks are the source, like alaskite, porphyritic leucogranites, aplite and rhyolite. Leucocratic facies of medium to coarse grained granitic intrusive bodies with only very minor or absent coarser grained mafic minerals (generally less than 5%). The mafic minerals must be in larger grains or aggregates for easy separation by a simple, preferably dry method. Such granitic rocks should have feldspar as the main constituent and silica subordinate or absent.

 

TECTONIC SETTINGS:  In orogenic belts, probably related to subduction related magmatism. High level, well differeniated bodies that crystallized slowly.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTINGHigh level magma emplacement in volcano-plutonic arcs, frequently in association with fields of pegmatite dikes.


AGE OF MINERALIZATIONEarly Paleozoic for the classical deposit, but can be part of any orogenic granitic complex.


HOST/ASSOCIATED ROCK TYPESPegmatite and granodiorite-granite-syenite intrusive rocks, commonly porphyritic / sedimentary and metamorphic rocks.


DEPOSIT FORMIntrusive bodies of irregular shape, in the classical area of North Carolina up to 1600 meters wide and 3200 metres long.

 

TEXTURE/STRUCTUREMassive, may have foliated appearance close to contacts, with inclusions of country rock. The grain size may vary, in the average about 1.25 centimetres in diameter , locally coarser near the intrusive`s center, but less then 0.5 centimetre near the contact. In the Spruce Pine district the post-magmatic recrystallization produced a “mortar-like” structure where relatively large grains of feldspar, quartz and muscovite 5 to 10 mm in diameter are enclosed in a fine-grained recrystallized matrix of feldspar, quartz and muscovite with epidote. (resulting from removal of Fe from muscovite).


ORE MINERALOGY [Principal and subordinate]The classical deposit has 40% oligoclase, 20% quartz, 20% microcline and 15% muscovite.


GANGUE MINERALOGY [Principal and subordinate]Biotite, garnet; apatite, allanite, epidote, thulite, pyrite and pyrrhotite. In general do not exceed in total some 5%. Reported Fe2O3 content of rock is 0.33%.

 

ALTERATION MINERALOGY:  Secondary albitization, sericite, epidote.


WEATHERING: Kaolinization of feldspar.
 

ORE CONTROLSUniformity of rock composition, particularly in feldspar/quartz relationship and quantity of iron containing minerals. Grain size and form of distribution of mafics and other accessories. Grain sizes are important to separate feldspar and quartz from mafic minerals within commercial sized particles (glass 20 – 100 mesh).

 
GENETIC MODELLate stage intrusion of alkali rich leucocratic magma into slowly cooling environment, sometimes in more than one stage. In case of Spruce Pine district the oligoclas/microcline composition of feldspars may suggest either very slow cooling or recrystallization. The rock structure of larger isometric grains in fine-grained matrix support the recrystallization idea. Also, the silica in Spruce Pine alaskite is almost free of fluid inclusions. The age of associated pegmatite field of 380 Ma is coincident with waning regional metamorphism. Postmagmatic recrystallization is also suspected for removal of many impurities (including fluid inclusions) from quartz grains.

 
ASSOCIATED DEPOSIT TYPES: Pegmatite deposits of feldspar, mica, beryl, lithium, REE.

 
COMMENTS: Feldspathic sands and gravels are an alternative source of Na, K, and Al in many regions worldwide. In British Columbia Scuzzy Creek (092HNW052) is an example of a feldspathic sand occurrence. Partially kaolinitized granites can successfully replace feldspar in some ceramic products.

 


EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATUREFeldspar and silica, no mafic minerals – High K, Na, Al, Si; low Fe, Mg, Ca.

 

GEOPHYSICAL SIGNATUREDepends on local geology. In some circumstances the feldspar-rich rock may have contrasting properties from the host rock – electric, magnetic, density, gamma – which could be used in geophysics to prospect for or explore an feldspathic target. Presence of Fe minerals may be contrasting in using the magnetic or IP methods.

 

 

OTHER EXPLORATION GUIDESResistance to weathering can be good prospecting tool in areas of weak host rocks.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGEUniformity of the rock is more important than relative content of Na, K, Al and Si. Important is the Fe2O3, which should be below 0.1%, and absence of refractory minerals like zircon, corundum or spinel. Also, the end use can make a difference – some industries prefer more potassic than sodium feldspar. In 2001, North America produced some 800,000 tonnes of feldspar, of which about half came from three alaskite production centers in North Carolina. Another 12%, of a potassic feldspar used for more special end uses came from the producer of leucogranite in Georgia. The bulk of the rest came from feldspathic sands and a small fraction as a co-product from pegmatites.


ECONOMIC LIMITATIONSFeldspar Corporation of Middletown, Connecticut shut down in 1991 its aplite processing plant, when its production capacity of 90,000 tonnes per year suffered the market reduction to 37% as a result of competition with nepheline syenite from Ontario sources. Feldspar, as all low priced bulk commodities is transportation sensitive, and feldspar resource in a variety of deposit types is distributed through many parts of North America.

 

END USES:  Main uses for feldspar is in glass (~60%) and ceramics (~35%) manufacturing. The remaining 5% is used as a specialty fillers, abrasives and some other minor uses. Very high purity silica (in the order of 10 to 100 ppm impurities) is very important co-product from Spruce Pine district, North Carolina, and is exported for high-tech product manufacturing globally (QUINTAs and IOTA grades).

 

IMPORTANCEProduction of glass and ceramics requires feldspar (or nepheline syenite). Alaskite and other feldspar-rich rocks is a very important resource, since the bodies are suitable for large scale, inexpensive mining and processing techniques. The deposits location is convenient for economic transportation to glass and ceramic plants in southeast USA. The high purity silica from Spruce Pine is the only major producer worldwide.

 

 

 REFERENCES

 

Bolger, R.B. (1995): Feldspar and Nepheline Syenite, Industrial Minerals, No. 332, May, page 25-45.

Brobst, D.A. (1991): Other Selected Industrial Minerals; in Gluskoter, H. J., Rice, D.D., and Taylor, R.G., Editors, Economic Geology, The Geology of North America, volume P-2, Geological Society of America, page 189-211.

Brobst, D.A. (1962): Geology of the Spruce Pine District Avery, Mitchell, and Yancey Counties North Carolina, U.S.Geological Survey, Bulletin 1122-A, 26 pages.

Feiss, P.G. and Slack, J.F. (1989): Mineral Deposits of the U.S. Appalachians; in Hatcher, R.D.,Jr., Thomas, W.A. and Viele, G.W. Editors, The Geology of North America, Volume F-2, Geological Society of America, page 471 –494.

Feitler, S.A. (1967): Feldspar Resources and Marketing in Eastern United States, U.S. Bureau of Mines, IC 8310, 41 pages.

Glover, A. (2006): The Spruce Mining District – A brief review of history, geology, and modern uses of the minerals mined in the Spruce Pine Mining District, Mitchell, Avery and Yancey Counties, North Carolina, in Reid, J.C., editor, Proceedings of the 42nd Forum on the Geology of Industrial Minerals: Information Circular 34, North Carolina Geological

Survey, Page 269 – 272.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals. A Global Geology. Metal Bulletin PLC, London, UK, 462 pages.

Kaufman, R.A. and Van Dyk, D. (1994): Feldspars; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, page 473-481.

MacLean, M.E. and White, G.V. (1991): Feldspatic Mineral Occurrences in British Columbia, B.C. Ministry of Energy, Mines and Petroleum Resources, Open File 1991-10, 88 pages.

Marmo, V. (1971): Granite Petrology and Granite Problem. Elsevier Publishing Company, Amsterdam, London, New York, 244 pages.

Potter, M.J. (2001): Feldspar and Nepheline Syenite; in Mineral Industry Surveys, U.S. Geological Survey, page 26.1-26.7

Potter, M.J. (2006): Feldspars; in  Kogel, J.E.,Trivedi, N.C., Barker, J. M. and Krukowski, S.T., Editors, Industrial Minerals and Rocks, Commodities, Markets and Uses, Society for Mining, Metallurgy and Exploration,Inc., Littleton, Colorado, page 451 – 460.

Swanson, S.E. and Veal, W.B. (2006): Texture: Its what makes Spruce Pine Granite Special, in Reid, J.C., editor, Proceedings of the 42nd Forum on the Geology of Industrial Minerals; Information Circular 34, North Carolina Geological Survey, pages 537 – 538. 

*  Note:  All BC deposit profile #s with an asterisk have no completed deposit profile.  USGS deposit model #s with an asterisk had no published model in the late 1990s. 

Examples of Industrial Rock Deposits

BC Profile # Global Examples B.C. Examples
R01 - - Dunsmuir shale, Sumas Mountain
R02 Wabamun shales (Alberta) Nanaimo shale, Saturna Island
R03 Riviére á Pierre (Québec), Black Hills (South Dakota) Nelson Island
R04 Vermont, Alabama, Georgia Marblehead, Anderson Bay (Texada Island)
R05 (covered in R03) - - Haddington Island
R06 - - Saturna Island, Newcastle Island
R07 - - Moberley, Nicholson
R08 Southowram (England) Salmo, Revelstoke
R09 - - Texada Island, Quatsino Belt
R10 - - Crawford Bay, Rock Creek
R11 - - Meagher Mountain, Buse Lake
R12 - - Frenier, Francois Lake
R13 Blue Mountain (Ontario) Trident Mountain
R14 Spruce Pine alaskite (North Carolina) - -
 R15* - - McAbbee, Gissome