![Sample of Quartzite](https://upload.wikimedia.org/wikipedia/commons/b/b8/Sample_of_Quartzite.JPG)
Quartzite is a hard, non-
foliated metamorphic rock
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causin ...
which was originally pure
quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
.
[Essentials of Geology, 3rd Edition, Stephen Marshak, p 182] Sandstone is converted into quartzite through heating and pressure usually related to
tectonic
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...
compression within
orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of
hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
. Other colors, such as yellow, green, blue and orange, are due to other minerals.
The term ''quartzite'' is also sometimes used for very hard but unmetamorphosed
sandstones
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) b ...
that are composed of quartz grains thoroughly cemented with additional quartz. Such sedimentary rock has come to be described as orthoquartzite to distinguish it from metamorphic quartzite, which is sometimes called metaquartzite to emphasize its metamorphic origins.
Quartzite is very resistant to chemical
weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
and often forms ridges and resistant hilltops. The nearly pure silica content of the rock provides little material for
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
; therefore, the quartzite ridges are often bare or covered only with a very thin layer of soil and little (if any) vegetation. Some quartzites contain just enough weather-susceptible nutrient-bearing minerals such as
carbonates and
chlorite
The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous ac ...
to form a loamy, fairly fertile though shallow and stony soil.
Quartzite has been used since prehistoric times for stone tools. It is presently used for decorative dimension stone, as crushed stone in highway construction, and as a source of
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
for production of
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
and silicon compounds.
Characteristics and origin
Quartzite is a very hard rock composed predominantly of an interlocking mosaic of quartz crystals. The grainy, sandpaper-like surface is glassy in appearance. Minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization, causing streaks and lenses to form within the quartzite.
[ To be classified as a quartzite by the ]British Geological Survey
The British Geological Survey (BGS) is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research.
The BGS h ...
, a metamorphic rock must contain at least 80% quartz by volume.
Quartzite is commonly regarded as metamorphic in origin.[ When sandstone is subjected to the great heat and pressure associated with regional metamorphism, the individual quartz grains recrystallize along with the former cementing material. Most or all of the original texture and sedimentary structures of the sandstone are erased by the metamorphism.][ The recrystallized quartz grains are roughly equal in size, forming what is called a granoblastic texture, and they also show signs of metamorphic annealing, in which the grains become coarser and acquire a more polygonal texture.][ The grains are so tightly interlocked that when the rock is broken, it fractures through the grains to form an irregular or conchoidal fracture.]
Geologists had recognized by 1941 that some rocks show the macroscopic characteristics of quartzite, even though they have not undergone metamorphism at high pressure and temperature. These rocks have been subject only to the much lower temperatures and pressures associated with diagenesis of sedimentary rock, but diagenesis has cemented the rock so thoroughly that microscopic examination is necessary to distinguish it from metamorphic quartize. The term ''orthoquartzite'' is used to distinguish such sedimentary rock from ''metaquartzite'' produced by metamorphism. By extension, the term ''orthoquartzite'' has occasionally been more generally applied to any quartz-cemented quartz arenite
A quartz arenite or quartzarenite is a sandstone composed of greater than 90% detrital quartz. Quartz arenites are the most mature sedimentary rocks possible, and are often referred to as ultra- or super-mature, and are usually cemented by sili ...
. Orthoquartzite (in the narrow sense) is often 99% SiO2 with only very minor amounts of iron oxide and trace resistant minerals such as zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...
, rutile and magnetite
Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...
. Although few fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s are normally present, the original texture and sedimentary
Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
structures are preserved.[
The typical distinction between a true orthoquartzite and an ordinary quartz sandstone is that an orthoquartzite is so highly cemented that it will fracture across grains, not around them.][ This is a distinction that can be recognized in the ]field
Field may refer to:
Expanses of open ground
* Field (agriculture), an area of land used for agricultural purposes
* Airfield, an aerodrome that lacks the infrastructure of an airport
* Battlefield
* Lawn, an area of mowed grass
* Meadow, a grass ...
. In turn, the distinction between an orthoquartzite and a metaquartzite is the onset of recrystallization of existing grains. The dividing line may be placed at the point where strained quartz grains begin to be replaced by new, unstrained, small quartz grains, producing a ''mortar texture'' that can be identified in thin sections under a polarizing microscope. With increasing grade of metamorphism, further recrystallization produces ''foam texture'', characterized by polygonal grains meeting at triple junctions, and then ''porphyroblastic texture'', characterized by coarse, irregular grains, including some larger grains ( porphyroblasts.)[
]
Occurrence
In the United States, formations of quartzite can be found in some parts of Pennsylvania, the Washington DC area, eastern South Dakota
South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...
, Central Texas, southwest Minnesota
Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...
, Devil's Lake State Park in the Baraboo Range
The Baraboo Range is a syncline located in Columbia and Sauk Counties, Wisconsin. It consists of highly eroded Precambrian metamorphic rock. It is about long and varies from 5 to in width. The Wisconsin River, previously traveling in a north ...
in Wisconsin
Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...
, the Wasatch Range in Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
, near Salt Lake City, Utah and as resistant ridges in the Appalachians and other mountain regions. Quartzite is also found in the Morenci Copper Mine in Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, AlÄ á¹£onak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
. The town of Quartzsite in western Arizona derives its name from the quartzites in the nearby mountains in both Arizona and Southeastern California. A glassy ''vitreous quartzite'' has been described from the Belt Supergroup
The Belt Supergroup is an assemblage of primarily fine-grained sedimentary rocks and mafic intrusive rocks of late Precambrian (Mesoproterozoic) age. It is more than thick, covers an area of some 200,000 km2 (77,220 sq. mi), and is considered ...
in the Coeur d’Alene district of northern Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...
.
In Canada, the La Cloche Mountains in Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
are composed primarily of white quartzite. Vast areas of Nova Scotia
Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland".
Most of the population are native Eng ...
are underlain by quartzite.
Paleoproterozoic quartzite-rhyolite
Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
successions are common in the Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pêž’, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
basement
A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...
rock of western North America. The quartzites in these successions are interpreted as sedimentary beds deposited atop older greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies.
The name comes from the green ...
s. The quartzite-rhyolite successions may record the formation of back-arc basins
A back-arc basin is a type of geologic Structural basin, basin, found at some convergent boundary, convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found ...
along the margin of Laurentia
Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although ...
, the ancient core of North America, between episodes of mountain building during the assembly of the continent. The quartzites are often nearly pure quartz, which is puzzling for sediments which must have eroded from igneous rock. Their purity may reflect unusual conditions of chemical weathering, at a time when the Earth's atmosphere was beginning to be oxygenated.
In Ireland
Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
areas of quartzite are found across the west and northwest, with Errigal in Donegal Donegal may refer to:
County Donegal, Ireland
* County Donegal, a county in the Republic of Ireland, part of the province of Ulster
* Donegal (town), a town in County Donegal in Ulster, Ireland
* Donegal Bay, an inlet in the northwest of Ireland b ...
as the most prominent outcrop. A good example of a quartzite area is on An Corrà n
An, AN, aN, or an may refer to:
Businesses and organizations
* Airlinair (IATA airline code AN)
* Alleanza Nazionale, a former political party in Italy
* AnimeNEXT, an annual anime convention located in New Jersey
* Anime North, a Canadian an ...
peninsula, in Co. Mayo
County Mayo (; ga, Contae Mhaigh Eo, meaning "Plain of the Taxus baccata, yew trees") is a Counties of Ireland, county in Republic of Ireland, Ireland. In the West Region, Ireland, West of Ireland, in the Provinces of Ireland, province of Conn ...
, which has a very thin layer of Irish Atlantic Bog covering it.
In the United Kingdom, a craggy ridge of quartzite called the Stiperstones
The Stiperstones ( cy, Carneddau Teon) is a distinctive hill in the county of Shropshire, England. The quartzite rock of the ridge formed some 480 million years ago. During the last Ice Age Stiperstones lay on the eastern margin of the Welsh i ...
(early Ordovician – Arenig Epoch, 500 Ma) runs parallel with the Pontesford-Linley fault, 6 km north-west of the Long Mynd in south Shropshire
Shropshire (; alternatively Salop; abbreviated in print only as Shrops; demonym Salopian ) is a landlocked historic county in the West Midlands region of England. It is bordered by Wales to the west and the English counties of Cheshire to th ...
. Also to be found in England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
are the Cambrian
The Cambrian Period ( ; sometimes symbolized C with bar, êž’) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
" Wrekin quartzite" (in Shropshire), and the Cambrian "Hartshill
Hartshill is a large village and civil parish in North Warwickshire, England, 2.5 miles (4 km) north-west of the town of Nuneaton. The parish borders the district of Nuneaton and Bedworth at the south, the North Warwickshire district parishes ...
quartzite" (Nuneaton
Nuneaton ( ) is a market town in the borough of Nuneaton and Bedworth in northern Warwickshire, England, close to the county border with Leicestershire and West Midlands County.OS Explorer Map 232 : Nuneaton & Tamworth: (1:25 000) : Nuneaton's ...
area). In Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
, Holyhead Mountain and most of Holy island
Sacred space, sacred ground, sacred place, sacred temple, holy ground, or holy place refers to a location which is deemed to be sacred or hallowed. The sacredness of a natural feature may accrue through tradition or be granted through a bless ...
off Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
sport excellent Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pêž’, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
quartzite crags and cliffs. In the Scottish Highlands
The Highlands ( sco, the Hielands; gd, a’ Ghà idhealtachd , 'the place of the Gaels') is a historical region of Scotland. Culturally, the Highlands and the Lowlands diverged from the Late Middle Ages into the modern period, when Lowland Sco ...
, several mountains (e.g. Foinaven, Arkle
Arkle (19 April 1957 – 31 May 1970) was an Irish Thoroughbred racehorse. A bay gelding by ''Archive'' out of ''Bright Cherry'', he was the grandson of the unbeaten (in 14 races) flat racehorse and prepotent sire Nearco. Arkle was bred by Mar ...
) composed of Cambrian quartzite can be found in the far north-west Moine Thrust Belt
The Moine Thrust Belt or Moine Thrust Zone is a linear tectonic feature in the Scottish Highlands which runs from Loch Eriboll on the north coast south-west to the Sleat peninsula on the Isle of Skye. The thrust belt consists of a series of t ...
running in a narrow band from Loch Eriboll in a south-westerly direction to Skye
The Isle of Skye, or simply Skye (; gd, An t-Eilean Sgitheanach or ; sco, Isle o Skye), is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous hub dominated b ...
.
In continental Europe
Continental Europe or mainland Europe is the contiguous continent of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by ...
, various regionally isolated quartzite deposits exist at surface level in a belt from the Rhenish Massif
The Rhenish Massif, Rhine Massif or Rhenish Uplands (german: Rheinisches Schiefergebirge, : 'Rhenish Slate Uplands') is a geologic massif in western Germany, eastern Belgium, Luxembourg and northeastern France. It is drained centrally, south to n ...
and the German Central Highlands into the Western Czech Republic
The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
, for example in the Taunus
The Taunus is a mountain range in Hesse, Germany, located north of Frankfurt. The tallest peak in the range is ''Großer Feldberg'' at 878 m; other notable peaks are ''Kleiner Feldberg'' (825 m) and ''Altkönig'' (798 m).
The Taunus range spans ...
and Harz
The Harz () is a highland area in northern Germany. It has the highest elevations for that region, and its rugged terrain extends across parts of Lower Saxony, Saxony-Anhalt, and Thuringia. The name ''Harz'' derives from the Middle High German ...
mountains. In Poland quartzite deposits at surface level exists in Świętokrzyskie Mountains. In Norway, deposits are quarried near Austertana
Austertana ( sme, Juovlavuotna) is a village in Deatnu-Tana Municipality in Troms og Finnmark county, Norway. The village is located along one of the inner bays of the large Tanafjorden, east of Rustefjelbma in northeastern Tana. The village is ...
, which is one of the largest quarries in the world at 850,000 metric tonnes) annually, and Mårnes near Sandhornøy with an output of 150,000 metric tonnes annually. Deposits are also quarried at Kragerø
Kragerø () is a List of cities in Norway, town and Municipalities of Norway, municipality in Vestfold og Telemark Counties of Norway, county, Norway. It is part of the Districts of Norway, traditional regions of Grenland and the smaller Vestmar. ...
, and several other deposits are known but not actively quarried.
The highest mountain in Mozambique
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
, Monte Binga (2436 m), as well as the rest of the surrounding Chimanimani Plateau are composed of very hard, pale grey, Precambrian quartzite. Quartzite is also mined in Brazil for use in kitchen countertops.
Uses
Quartzite is a decorative stone and may be used to cover walls, as roofing tiles, as flooring, and stairsteps. Its use for countertops in kitchens is expanding rapidly. It is harder and more resistant to stains than granite. Crushed quartzite is sometimes used in road construction. High purity quartzite is used to produce ferrosilicon, industrial silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
sand, silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
and silicon carbide.
During the Paleolithic
The Paleolithic or Palaeolithic (), also called the Old Stone Age (from Greek: παλαιός ''palaios'', "old" and λίθος ''lithos'', "stone"), is a period in human prehistory that is distinguished by the original development of stone too ...
, quartzite was used, along with flint
Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start fir ...
, quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
, and other lithic raw materials, for making stone tools.
Safety
As quartzite is a form of silica, it is a possible cause for concern in various workplaces. Cutting, grinding, chipping, sanding, drilling, and polishing natural and manufactured stone products can release hazardous levels of very small, crystalline silica dust particles into the air that workers breathe. Crystalline silica of respirable size is a recognized human carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
and may lead to other diseases of the lungs such as silicosis
Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis. Silicos ...
and pulmonary fibrosis.
Etymology
The term ''quartzite'' is derived from german: Quarzit.
File:SwanPeakQuartziteOutcrop.jpg, Swan Peak Quartzite ( Ordovician) exposed just north of Tony Grove Lake
Tony Grove Lake is a lake in Cache County, Utah. The Tony Grove Lake Campground is located on the southeast shore of the lake. The lake and campground are situated on the Logan Canyon Scenic Byway. A paved road climbs to a height of to reach ...
, Cache County, Utah
Cache County ( ) is a county located in the Wasatch Front region of Utah. As of the 2020 United States Census the population was 133,154. Its county seat and largest city is Logan. Cache County is included in Logan metropolitan area.
History ...
File:View_of_Doso_Doyabi_from_Wheeler_Peak.jpg, The quartzite of the Prospect Mountain Formation
Prospect may refer to:
General
* Prospect (marketing), a marketing term describing a potential customer
* Prospect (sports), any player whose rights are owned by a professional team, but who has yet to play a game for the team
* Prospect (mini ...
at the top of Doso Doyabi in White Pine County, Nevada
White Pine County is a largely rural, mountain county along the central eastern boundary of the U.S. state of Nevada. As of the 2010 census, the population was 10,030. Its county seat is Ely. The name "(Rocky Mountain) white pine" is an old ...
Image:Normal view of Bo Quartzite.JPG, Quartzite from Salangen
Salangen is a municipality in Troms og Finnmark county, Norway. The administrative centre of the municipality is the village of Sjøvegan, where most of the people in the municipality live. Other villages include Elvenes, Laberg, and Seljesko ...
, South Troms, Norway, showing elongate crystals associated with high strain regimes
Image:Thin section image of quartzie.jpg, Thin section of quartzite from Salangen, South Troms, Norway, showing elongate crystals associated with high strain regimes
See also
* Neomorphism
References
External links
R. V. Dietrich's GemRocks: Quartzite
* ttps://web.archive.org/web/20100309140357/http://www.dnr.state.mn.us/snas/naturalhistory.html Minnesota Department of Natural Resources : Natural History: Minnesota's geology
Wisconsin's Baraboo Syncline (map and aerial photos of Baraboo quartzite quarries)
South Dakota 2002 Mineral Summary: Production, Exploration and Environmental Issues (including 2002 quartzite production)
{{Authority control
Quartz varieties
Metasedimentary rocks