A rock formed from the metamorphism of quartz sandstone.
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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.
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. Quartzites often occur in various shades of pink and red due to varying amounts of iron oxide. Other colors are due to impurities of minor amounts of other minerals.
In true metamorphic quartzite, also called meta-quartzite, the individual quartz grains have recrystallized along with the former cementing material to form an interlocking mosaic of quartz crystals. Minor amounts of former cementing materials, iron oxide, carbonate and clay, are often recrystallized and have migrated under the pressure to form streaks and lenses within the quartzite. Virtually all original textures and structure have usually been erased by the metamorphism.
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.
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.
Because of its hardness, about 7 on Mohs' scale of mineral hardness,[3][4] crushed quartzite is often used as railway ballast.[5][6] In the United States, formations of quartzite can be found in eastern South Dakota,[7] southwest Minnesota,[8] the Baraboo Hills in Wisconsin,[9] the Wasatch Range in Utah,[10] near Salt Lake City, Utah and as resistant ridges in the Appalachians[11] and other mountain regions. Quartzite is also found in the Morenci Copper Mine in Arizona.[12] The town of Quartzsite in western Arizona derives its name from the quartzites in the nearby mountains.
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