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34-606: The Pocono is also a lateral equivalent of the Purslane Sandstone in Maryland and West Virginia. D. Brezinski of Maryland Geological Survey recommended abandoning use of the term Pocono in Maryland in favor of "Purslane" in 1989. The Pocono is a dominantly gray color with quartzitic medium to coarse-grained sandstones . The base of the Pocono Formation is marked by conglomerate . Relative age dating of

68-467: A role as sediments become buried much deeper in the Earth's crust . In the early stages, the transformation of poorly consolidated sediments into sedimentary rock ( lithification ) is simply accompanied by a reduction in porosity and water expulsion ( clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content

102-1043: A very thin layer of Irish Atlantic Bog covering it. 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 . Also to be found in England are the Cambrian " Wrekin quartzite" (in Shropshire), and the Cambrian " Hartshill quartzite" ( Nuneaton area). In Wales , Holyhead Mountain and most of Holy island off Anglesey sport excellent Precambrian quartzite crags and cliffs. In

136-563: Is a stub . You can help Misplaced Pages by expanding it . Quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone . 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 hematite . Other colors, such as yellow, green, blue and orange, are due to other minerals. The term quartzite

170-401: 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 and may lead to other diseases of

204-479: Is also sometimes used for very hard but unmetamorphosed sandstones 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 and often forms ridges and resistant hilltops. The nearly pure silica content of

238-410: Is buried during sedimentation, the constituent organic molecules ( lipids , proteins , carbohydrates and lignin - humic compounds) break down due to the increase in temperature and pressure . This transformation occurs in the first few hundred meters of burial and results in the creation of two primary products: kerogens and bitumens . It is generally accepted that hydrocarbons are formed by

272-508: Is extensively used in geology . However, this term has filtered into the field of anthropology , archaeology and paleontology to describe the changes and alterations that take place on skeletal (biological) material. Specifically, diagenesis "is the cumulative physical, chemical, and biological environment; these processes will modify an organic object's original chemical and/or structural properties and will govern its ultimate fate, in terms of preservation or destruction". In order to assess

306-498: Is presently used for decorative dimension stone, as crushed stone in highway construction, and as a source of silica for production of silicon and silicon compounds. 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

340-919: Is progressively transformed into kerogens and bitumens . The process of diagenesis excludes surface alteration ( weathering ) and deep metamorphism . There is no sharp boundary between diagenesis and metamorphism , but the latter occurs at higher temperatures and pressures . Hydrothermal solutions, meteoric groundwater, rock porosity, permeability , dissolution/ precipitation reactions , and time are all influential factors. After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution . Grains of sediment, rock fragments and fossils can be replaced by other minerals (e.g. calcite , siderite , pyrite or marcasite ) during diagenesis. Porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization . The study of diagenesis in rocks

374-681: 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 areas of quartzite are found across the west and northwest, with Errigal in County Donegal as the most prominent outcrop. A good example of a quartzite area is on the Corraun Peninsula in County Mayo , which has

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408-464: Is sometimes used in road construction. High purity quartzite is used to produce ferrosilicon , industrial silica sand, silicon and silicon carbide . During the Paleolithic , quartzite was used, along with flint , quartz , and other lithic raw materials, for making stone tools . Prehistoric humans in the southeastern United States often made mortars out of quartzite stones. As quartzite

442-427: Is used to understand the geologic history they have undergone and the nature and type of fluids that have circulated through them. From a commercial standpoint, such studies aid in assessing the likelihood of finding various economically viable mineral and hydrocarbon deposits. The process of diagenesis is also important in the decomposition of bone tissue. The term diagenesis, literally meaning "across generation",

476-507: The Precambrian basement rock of western North America. The quartzites in these successions are interpreted as sedimentary beds deposited atop older greenstone belts . The quartzite-rhyolite successions may record the formation of back-arc basins along the margin of Laurentia , 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

510-622: The Scottish Highlands , several mountains (e.g. Foinaven , Arkle ) composed of Cambrian quartzite can be found in the far north-west Moine Thrust Belt running in a narrow band from Loch Eriboll in a south-westerly direction to Skye . In continental Europe , various regionally isolated quartzite deposits exist at surface level in a belt from the Rhenish Massif and the German Central Highlands into

544-903: The Morenci Copper Mine in Arizona . 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 . In Canada, the La Cloche Mountains in Ontario are composed primarily of white quartzite. Vast areas of Nova Scotia are underlain by quartzite. Paleoproterozoic quartzite- rhyolite successions are common in

578-716: The Pocono places it in the lower Mississippian period. The lower boundary is with the Spetchy Kopf Formation and Huntley Mountain Formation . In South-central Pennsylvania, the Pocono often interfingers with the Rockwell Formation . [REDACTED] Media related to Pocono Formation at Wikimedia Commons This article about a specific stratigraphic formation in the United States

612-753: The United States, formations of quartzite can be found in some parts of Pennsylvania, the Washington DC area, eastern South Dakota , Central Texas, southwest Minnesota , Devil's Lake State Park in the Baraboo Range in Wisconsin , the Wasatch Range in Utah , near Salt Lake City, Utah and as resistant ridges in the Appalachians and other mountain regions. Quartzite is also found in

646-899: The Western Czech Republic , for example in the Taunus and Harz mountains. In Poland, quartzite deposits at surface level exists in Świętokrzyskie Mountains . In Norway, deposits are quarried near Austertana , which is one of the largest quarries in the world at 850,000 tonnes (840,000 long tons; 940,000 short tons) annually, and Mårnes near Sandhornøya with an output of 150,000 tonnes (150,000 long tons; 170,000 short tons) annually. Deposits are also quarried in Kragerø Municipality , and several other deposits are known but not actively quarried. The highest mountain in Mozambique , Monte Binga (2436 m), as well as

680-503: The dissolution-precipitation mechanism. These models have been intensively studied and applied in real geological applications. Diagenesis has been divided, based on hydrocarbon and coal genesis into: eodiagenesis (early), mesodiagenesis (middle) and telodiagenesis (late). During the early or eodiagenesis stage shales lose pore water, little to no hydrocarbons are formed and coal varies between lignite and sub-bituminous . During mesodiagenesis, dehydration of clay minerals occurs,

714-400: The form of hydroxyapatite ) renders its diagenesis more complex. Alteration occurs at all scales from molecular loss and substitution, through crystallite reorganization, porosity, and microstructural changes, and in many cases, to the disintegration of the complete unit. Three general pathways of the diagenesis of bone have been identified: They are as follows: When animal or plant matter

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748-401: 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

782-442: The lungs such as silicosis and pulmonary fibrosis . The term quartzite is derived from German : Quarzit . Diagenesis Diagenesis ( / ˌ d aɪ . ə ˈ dʒ ɛ n ə s ɪ s / ) is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition . Increased pressure and temperature only start to play

816-441: The main development of oil genesis occurs and high to low volatile bituminous coals are formed. During telodiagenesis, organic matter undergoes cracking and dry gas is produced; semi- anthracite coals develop. Early diagenesis in newly formed aquatic sediments is mediated by microorganisms using different electron acceptors as part of their metabolism. Organic matter is mineralized, liberating gaseous carbon dioxide (CO 2 ) in

850-479: The original texture and sedimentary 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 . 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

884-418: 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

918-487: 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 ). In

952-470: The porewater, which, depending on the conditions, can diffuse into the water column. The various processes of mineralization in this phase are nitrification and denitrification , manganese oxide reduction, iron hydroxide reduction, sulfate reduction , and fermentation . Diagenesis alters the proportions of organic collagen and inorganic components (hydroxyapatite, calcium, magnesium) of bone exposed to environmental conditions, especially moisture. This

986-418: The potential impact of diagenesis on archaeological or fossil bones , many factors need to be assessed, beginning with elemental and mineralogical composition of bone and enveloping soil, as well as the local burial environment (geology, climatology , groundwater ). The composite nature of bone, comprising one-third organic (mainly protein collagen ) and two thirds mineral ( calcium phosphate mostly in

1020-484: The quartzite. To be classified as a quartzite by the British Geological Survey , 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

1054-472: 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. 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

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1088-422: The rock provides little material for soil ; 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 to form a loamy, fairly fertile though shallow and stony soil. Quartzite has been used since prehistoric times for stone tools. It

1122-573: 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 . Orthoquartzite (in the narrow sense) is often 99% SiO 2 with only very minor amounts of iron oxide and trace resistant minerals such as zircon , rutile and magnetite . Although few fossils are normally present,

1156-431: The thermal alteration of these kerogens (the biogenic theory). In this way, given certain conditions (which are largely temperature-dependent) kerogens will break down to form hydrocarbons through a chemical process known as cracking , or catagenesis . A kinetic model based on experimental data can capture most of the essential transformation in diagenesis, and a mathematical model in a compacting porous medium to model

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