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quartz·ite (kwôrt'sīt') ![]() |
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A metamorphic rock consisting largely or entirely of quartz. Most quartzites are formed by metamorphism of sandstone; but some have developed by metasomatic introduction of quartz,SiO2, often accompanied by other chemical elements, for example, metals and sulfur (ore quartzites). See also Metamorphic rocks; Metasomatism; Sandstone.
Pure sandstones yield pure quartzites. Impure sandstones yield a variety of quartzite types.The cement of the original sandstone is in quartzite recrystallized into characteristic silicate minerals, whose composition often reflects the mode of development. Even the Precambrian quartzites correspond to types that are parallel to present-day deposits. See also Quartz.
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A variety of sandstone composed largely of granular quartz which is cemented by silica forming a homogeneous mass of very high tensile and crushing strengths; esp. used as a building stone, as gravel in road construction, and as an aggregate in concrete.
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| Wikipedia: Quartzite |
Quartzite (from German Quarzit[1]) is a hard metamorphic rock which was originally sandstone.[2] Sandstone is converted into quartzite through heating and pressure usually related to tectonic 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 iron oxide (Fe2O3). Other colors, such as yellow and orange, are due to other mineral impurities.
When sandstone is metamorphosed to quartzite, the individual quartz grains recrystallize along with the former cementing material to form an interlocking mosaic of quartz crystals. Most or all of the original texture and sedimentary structures of the sandstone are erased by the metamorphism. Minor amounts of former cementing materials, iron oxide, carbonate and clay, often migrate during recrystallization and metamorphosis. This causes streaks and lenses to form within the quartzite.
Orthoquartzite is a very pure quartz sandstone composed of usually well rounded quartz grains cemented by silica. Orthoquartzite is often 99% SiO2 with only very minor amounts of iron oxide and trace resistant minerals such as zircon, rutile and magnetite. Although few fossils are normally present, the original texture and sedimentary structures are preserved. The term is often misused, and should be used for only tightly-cemented metamorphic quartzites, not quartz-cemented quartz arenites[3]. The typical distinction between the two (since each is a gradation into the other) is a proper quartzite is so highly cemented, diagentically altered, and metamorphosed that it will fracture and break across grain boundaries, not around them.
Quartzite is very resistant to chemical weathering and often forms ridges and resistant hilltops. The nearly pure silica content of the rock provides little to form soil from and therefore the quartzite ridges are often bare or covered only with a very thin soil and little vegetation.
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Quartzite is a decorative stone and may be used to cover walls, as roofing tiles, as flooring, and stair steps. Crushed quartzite is sometimes used in road construction and for railway ballast.[2] High purity quartzite is used to produce ferrosilicon, industrial silica sand, silicon metal and silicon carbide.[4]
In the United States, formations of quartzite can be found in some parts of Pennsylvania, eastern South Dakota, Central Texas,[5] southwest Minnesota,[6] Devil's Lake State Park in the Baraboo Hills in Wisconsin,[7] the Wasatch Range in Utah,[8] near Salt Lake City, Utah and as resistant ridges in the Appalachians[9] and other mountain regions. Quartzite is also found in the Morenci Copper Mine in Arizona.[10] 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 in the Coeur d’Alene district of northern Idaho.[11]
In the United Kingdom, a craggy ridge of quartzite called the Stiperstones (early Ordovician - Arenig Epoch, 500 Ma) runs parallel with the Pontesford-Linley fault 6 km north-west of the Long Mynd in south Shropshire. Holyhead mountain and most of Holy island off Anglesey sport excellent Quartzite crags and cliffs. In the Scottish Highlands, several mountains composed of quartzite can be found in the far north-west Moine Thrust Belt (e.g. Foinaven, Arkle)
In Canada, the La Cloche Mountains in Ontario are composed primarily of white quartzite.
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![]() | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more | |
![]() | Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more | |
![]() | Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more | |
![]() | Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved. Read more | |
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