Sedimentary rocks are known as stratified rocks because of their distinctive stratification, unlike other types of rocks. Sedimentary rocks can be distinguished by color, particle size, cement type, or internal placement. Sedimentary rocks are categorized by age, and various types of rocks formed during the same period are grouped. Most of the …Chert is a biochemical sedimentary rock made from microcrystalline quartz. It is very hard – registering a 7 on the Mohs hardness scale, and displays conchoidal fracturing. Chert can almost any color, but is usually gray, brown, red, or green. It has many subvarieties including flint, jasper, agate, and onyx.... sedimentary rock that breaks with a conchoidal fracture. It is a form of microcrystalline quartz that is typically called "chert" by geologists. It often ...What is Chert? Chert is a sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO 2). It occurs as nodules, concretionary masses, and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges.Sedimentary rocks are formed in four ways: Debris from mechanical erosion of soils and rocks then transported and deposited as sediments. Chemical and biochemical processes. ... Another kind of chemical sedimentary rock is chert or flint (consisting of micro or crypto-crystalline silica) that sometimes probably originated from precipitation in ...FLINT AND CHERT FLINT: - dark colored sedimentary rock of siliceous composition - consists mainly of chalcedony and fine- grained quartz - occurs commonly as concretions or nodules in chalk (limestone) deposits CHERT: - composed of cryptocrystalline silica - variety of colors - occurs as beds or layers within limestones and …Chert has four diagnostic features: the waxy luster, a conchoidal (shell-shaped) fracture of the silica mineral chalcedony that composes it, a hardness of seven on the Mohs scale, and a smooth (non-clastic) sedimentary texture. Many types of chert fit into this categorization. 01 of 16 Flint Nodule James St. John/Wikimedia Commons/CC BY 2.0Sedimentary rocks make up only 5% (by volume) of the upper 10 miles of the crust, but about 75% of the outcrops on the continents. Two primary types of sedimentary rocks: ... Chert - a variety of cryptocrystalline (no crystal structure) silica; formed by the precipitation of silica from solution. Flint: a variety of chert which is dark owing to the presence of …Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils.In thin section the chert is a heterogeneous mixture of finely crystalline quartz, later porosity fillings, and many fragments of plants. There is some evidence ...Chert is a sedimentary rock with refined grains which is made of microcrystalline quartz, which is in the form of silicon oxide. It mainly occurs organically, but can also form inorganically through chemical precipitate. It mainly occurs in the beds of limestone. Color.Quartz schists are generally considered to be metamorphic derivatives of highly siliceous sedimentary rocks, cherts, although the sharp distinction between ...Sedimentary rocks of these kinds are very common in arid lands such as the deposits of salts and gypsum. Examples include rock salt, dolomites, flint, iron ore, chert, and some limestone. Organic Sedimentary Rocks: Organic sedimentary rocks are formed from the accumulation of any animal or plant debris such as shells and bones. These plant and ...Chert is a fine-grained and hard sedimentary rock that usually has a biological origin. Chert can also exist inorganically as a chemical precipitate or diagenetic replacement in petrified wood. Chert can be of various colors due to trace elements in the rock.Make sure to use all of the tools available including the glass plate and the diluted HCl to identify the chemical and biochemical sedimentary rocks (chert will be harder than glass, limestone will strongly react with dilute HCl, and dolostone will weakly react with dilute HCl when powdered).Oolite or oölite (from Ancient Greek ᾠόν (ōión) 'egg stone') [1] is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. [2] Strictly, oolites consist of ooids of diameter 0.25–2 millimetres; rocks composed of ooids larger than 2 mm are called pisolites. The term oolith can refer to oolite or individual ...Chert is a very hard sedimentary rock that is usually found in nodules in limestone. Chert is light gray to dark gray in color. It probably formed from the ...The most common chemical sedimentary rock, by far, is limestone. Others include chert, banded iron formation, and a variety of rocks that form when bodies of water evaporate. Biological processes are important in the formation of some chemical sedimentary rocks, especially limestone and chert. For example, limestone is made up almost entirely ...Find out some tips how to deal with drilling a water well through rock, and what to do it you hit rock while drilling. Expert Advice On Improving Your Home Videos Latest View All Guides Latest View All Radio Show Latest View All Podcast Epi...Deposits of chert formed from the accumulation of siliceous skeletons from microscopic organisms such as radiolaria and diatoms. Erosion ,Transport and ...Sedimentary rocks are characterised by their formation from the deposition and lithification of rock material. They may be formed through physical and chemical processes, such as mechanical weathering, compaction and dissolving of rock mate...What is Chert? Chert as a geologic formation is a sedimentary rock that can serve as a reservoir for oil and gas. For example, in West Virginia, a large pocket of natural gas occurs within such as the rock formation, known as the Huntersville Chert. Chert can take on various colors. Gray is common, as is white and pink.Chert chert – sedimentary rock. Chert is a sedimentary rock that’s been used by humans as a tool or building material since time immemorial. It is mostly comprised of quartz and it can also form through the petrification of wood. Many cherts are white or black in color, but you can find cherts in nearly any color imaginable. Usually, the color of …Gravel forms coarse rocks with grains over 2 mm in size. If the fragments are rounded, they form conglomerate, and if they are angular, they form breccia. Sand, as you may guess, forms sandstone. Sandstone is medium-grained, meaning its fragments are between 1/16 mm and 2 mm. Silt forms fine-grained siltstone, with fragments between …1.1.1 Chert is the general term for very fine-grained and nonporous sedimentary rocks that consist mostly or entirely of silica, in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The non-scientific equivalent term is flint. 1.1.2 Cherts are fairly easy to identify ...Rocks and minerals can be easily identified once you know what to look for. There are three different types of rocks: Igneous, Metamorphic and Sedimentary. Minerals must meet several requirements, including being naturally occurring and ino...Chert, another commonly found chemical sedimentary rock, is usually produced from silica (SiO 2) precipitated from groundwater. Silica is highly insoluble on the surface of Earth, which is why quartz is so resistant to chemical weathering.Chert and flint, very fine-grained quartz (q.v.), a silica mineral with minor impurities. Several varieties are included under the general term chert: jasper, chalcedony, agate (qq.v.), flint, porcelanite, and novaculite. Flint is gray to black and nearly opaque (translucent brown in thinPhotomicrographs of chert-replaced and cemented sedimentary rocks in thin section. (A) Silicified oolite in PPL (plane polarized light). (B) Same view as (A) in XPL (cross polarized light) showing a variety of silica cement and replacement fabrics after the original carbonate sediment. Trenton Series, Ordovician, Centre County, Pennsylvania, USA. (C) Silicified …Type Sedimentary Rock Origin Chemical-Biochemical Texture Nonclastic; Very fine-grained Composition Silica or Microcrystalline Quartz Color Tan to light gray Miscellaneous Microcrystalline; Hardness > Glass Depositional Environment Deep MarineSedimentary rocks are known as stratified rocks because of their distinctive stratification, unlike other types of rocks. Sedimentary rocks can be distinguished by color, particle size, cement type, or internal placement. Sedimentary rocks are categorized by age, and various types of rocks formed during the same period are grouped. Most of the …Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. ... Deposits of chert formed from the accumulation of siliceous skeletons of microscopic organisms …Sedimentary rocks are known as stratified rocks because of their distinctive stratification, unlike other types of rocks. Sedimentary rocks can be distinguished by color, particle size, cement type, or internal placement. Sedimentary rocks are categorized by age, and various types of rocks formed during the same period are grouped. Most of the …carbonate biochemical sedimentary rocks. Chert is a rock composed of microcrystalline varieties of quartz, and thus it has properties that are associated with quartz itself, such as conchoidal fracturing and hardness greater than glass. Chert is often formed deep in the ocean from silicious material that is either inorganic (e.g., silica clay) or biologic (e.g., …What is Chert? Chert is a sedimentary rock, mostly composed of silica. It is formed in the sediment precursors of limestone and chalk, mostly produced on the ocean floor. Microscopic organisms in the ocean have skeletons made of silica, which fall to the bottom of the ocean, dissolve, re-crystalize, and then petrify into chert. Because of the …Chert chert – sedimentary rock. Chert is a sedimentary rock that’s been used by humans as a tool or building material since time immemorial. It is mostly comprised of quartz and it can also form through the petrification of wood. Many cherts are white or black in color, but you can find cherts in nearly any color imaginable. Usually, the color of …7.4.7: Chert. Chert is a fine-grained (microcrystalline) variety of quartz. It is also the name given to rock composed primarily of fine-grained quartz. So, the name is used in two ways. Chert (the silica mineral kind) may be massive or layered. It is often in nodules or concretions in limestone. Some chert forms by recrystallization of ...28 ก.พ. 2558 ... Chert is a sedimentary rock rich in silica. Franciscan chert is formed from the tiny silica shells (0.5-1 mm) of marine plankton called ...Chert is a hard and compact sedimentary rock, consisting dominantly of very small quartz crystals. It is a common rock type which occurs mostly in carbonate rocks either in nodular form or in layers (bedded chert). Flint on the coast at Stevns Klint in Denmark. Chert is a fine-grained sedimentary rock composed of quartz (SiO2) that is microcrystalline or cryptocrystalline quartz. It is usually organic rock but also occur inorganically as a chemical precipitate or a diagenetic replacement. It occurs as nodules, concretionary masses, and as layered deposits.Clastic Sedimentary Rocks. How Clastic Sedimentary Rocks are Formed: Pre‑existing rock undergoes chemical and mechanical weathering by roots, acid rainwater, gravity, wind, and water. The broken particles are carried through water or air until they settle out in a lower area when the current wasn’t fast enough to carry the particles. 1.1.1 Chert is the general term for very fine-grained and nonporous sedimentary rocks that consist mostly or entirely of silica, in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The non-scientific equivalent term is flint. 1.1.2 Cherts are fairly easy to identify ...Chert is a sedimentary rock in the class known as chemical sedimentary rocks. It is composed of microcrystalline quartz. Chemical Sedimentary Rocks: Group: Texture: Composition: Rock Name: Inorganic: Nonclastic: Microcrystalline quartz, SiO 2: Chert: Biochemical: Nonclastic: Microcrystalline quartz, SiO 2: Chert: Chert is very hard and …Siliceous sedimentary rocks are fine-grained, dense, very hard rocks composed of the SiO2 minerals quartz, chalcedony, and opal. Chert is the general group name ...You have 99 problems and Chert isn’t one of them. This relatively common rock is found worldwide and it comes in limitless colors and varieties. Despite the stone’s popularity, there are many misconceptions about Chert. Chert is a sedimentary rock comprised of microcrystalline Quartz which makes it fairly hard, 7 on the Mohs Hardness …Classes of sedimentary rocks. Geologists divide sedimentary rocks into four major classes, based on their mode of origin. (1) Clastic sedimentary rock consists of cemented-together clasts, solid fragments and grains broken off of preexisting rocks (the word comes from the Greek klastos, meaning broken); (2) biochemical sedimentary …Biochemical Sedimentary Rocks Chert is composed of quartz and is found as nodules in limestone, or in distinct layers where it is composed of the microscopic shells of tiny marine organisms. Coal consists of the compressed, altered remains of land plants that occupied swamps and bogs. Chert Coal Wicander & Monroe (2002) Sedimentary facies formation …In sedimentary rocks, the silica in flint is usually of biogenic origin: countless skeletons of tiny marine organisms, like radiolaria, foraminiferes, or diatoms that have sedimented on the ocean floor and are slowly buried under more chalk, silica and organic ooze. ... Chert as a rock-forming material is described in the chapter Quartz as a ...Chemical sedimentary rocks form when dissolved materials preciptate from solution. Examples include: chert, some dolomites, flint, iron ore, limestones, and rock salt. Organic sedimentary rocks form from the accumulation of plant or animal debris. Examples include: chalk, coal, diatomite, some dolomites, and some limestones. Chert can be a chemical sedimentary rock, often forming as beds within limestone (Figure 5.14), or as irregular lenses or blobs (nodules). It can also be biochemical. Some tiny marine organisms (e.g., diatoms and radiolaria) make their tests from silica. When they die their tiny shells (or tests) settle slowly to the bottom of the lake or ocean, where they accumulate …Siliceous rocks are sedimentary rocks that consist of SiO 2, either in the form of amorphous silica (opal) or microcrystalline, cryptocrystalline quartz or chalcedony.These rocks are generally referred to as cherts. Chert is …Chemical sedimentary rocks are identified by identifying the mineral from which they are composed. In this lab there are four minerals that need to be identified - quartz, halite, gypsum and calcite. Quartz has a hardness of 7 and is very difficult to scratch, even with a good quality knife blade. Gypsum is relatively soft (Hardness =2) and can ...But how about when the chert forms the greater part of the rock? ... Some of the very oldest sedimentary rocks, in greenstone terranes, are bedded cherts.Sedimentary. Igneous rocks, such as granite and basalt, are formed directly from magma and lava. By contrast, metamorphic rocks like slate and gneiss are created when igneous, metamorphic, and ...5 มี.ค. 2564 ... ... sedimentary environment of the chert (Murray et al. ... rocks, indicating that the rocks did not undergo obvious sedimentary sorting and recycling ...Price: $4.29. SKU: SED9053. Add to Cart. Chert is a cryptocrystalline form of quartz that forms as nodules and layers within other sedimentary rocks such as dolomite, limestone and chalk. Chert is a sedimentary rock although it is often referred to as a mineral. Chert samples exist worldwide and are a common material for prehistoric arrowheads ... 🌄 Sedimentary Rock EXAMPLES. Arkose: Arkose is a type of sandstone with abundant feldspar grains. It forms in mountainous regions and is often associated with riverbeds. Evaporites: Evaporites include rocks like rock salt and gypsum and originate from the evaporation of water in environments like salt flats and playas. Chert: Chert is a …Chert is a sedimentary rock composed mostly of the mineral chalcedony—cryptocrystalline silica in crystals of submicroscopic size. This type of sedimentary rock can form in parts of the deep sea where the tiny shells of siliceous organisms are concentrated, or elsewhere where underground fluids replace sediments with silica. ...Chert is a fine-grained sedimentary rock composed of quartz (SiO2) that is microcrystalline or cryptocrystalline quartz. It is usually organic rock but also occur inorganically as a chemical precipitate or a diagenetic replacement. It occurs as nodules, concretionary masses, and as layered deposits.Note quartz mosaic in chert region. Age. Early Carboniferous. Location. Carboniferous Limestone Skyes, Bowland, Yorkshire. Hand ...Chert ( / ˈtʃɜːrt /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2 ). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. [3]D. Classification of Sedimentary Rocks from Composition: 1. Sandstone: Sandstone is rock made of particles of sand of size up to 2 mm. In most cases it is made of rounded particles of quartz but it can contain feldspar and even fragments of rock. Sandstone is a very commonly occurring sedimentary rock.The red variety of chert is called jasper. Dark gray to black chert is called flint. • The carbon-rich rock formed from ancient plant material is called coal. Sedimentary rocks with non-clastic texture include fossiliferous limestone (above left), chert (above right) and coal (right). All three of these rock types can be found in Virginia.siliceous rock, any of a group of sedimentary rocks that consist largely or almost entirely of silicon dioxide (SiO 2), either as quartz or as amorphous silica and cristobalite; included are rocks that have formed as chemical precipitates and excluded are those of detrital or fragmental origin.. The most common siliceous rock is chert, which is a dense, …Chert ( / ˈtʃɜːrt /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2 ). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. [3]Metamorphic rocks are generally a modified form of Igneous, Sedimentary, or previous Metamorphic rock by various external weather conditions like temperature, pressure, volume, etc. and for such reason, the appearance, texture, and composition of rocks were changed from the previous characteristics.Rocks: Igneous, Metamorphic and Sedimentary Rocks hold the history of the earth and the materials that will be used to build its future. Igneous. Igneous Rocks: Photos, descriptions and facts about intrusive and extrusive igneous rocks. Andesite. Basalt. Dacite. Diabase. Diorite. Gabbro. Granite. ... Flint, Chert, Jasper. Flint, Chert, and Jasper are …Oolite. Oolite is a sedimentary rock made up of ooids (ooliths) that are cemented together. Most oolites are limestones — ooids are made of calcium carbonate (minerals aragonite or calcite ). Ooids are spheroidal grains with a nucleus and mineral cortex accreted around it which increases in sphericity with distance from the nucleus.The most-important kinds of authigenic rocks are (1) chert, (2) phosphate rock, and (3) sedimentary iron ores. Evaporites formed by precipitation in the interstitial waters of a preexisting sediment likewise qualify as being authigenic. Chert. Chert is a tough, brittle siliceous rock exhibiting a splintery-to conchoidal fracture and a vitreous ...Minerals produced by chemical precipitation include clays, carbonates, sulfates, halides, zeolites, and chert. We name clastic sedimentary rocks based primarily ...Rock Field News: This is the News-site for the company Rock Field on Markets Insider Indices Commodities Currencies StocksChemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate. Common chemical sedimentary rocks include oolitic limestone and rocks composed of …Classes of sedimentary rocks. Geologists divide sedimentary rocks into four major classes, based on their mode of origin. (1) Clastic sedimentary rock consists of cemented-together clasts, solid fragments and grains broken off of preexisting rocks (the word comes from the Greek klastos, meaning broken); (2) biochemical sedimentary …Sedimentary rocks are rocks made by sediment that has accumulated over millions of years. This sediment can accumulate on the surface of the Earth or under water. Sedimentary rocks tend to resemble the sediment that created them, so they ar...Chert is also the name given to hard sedimentary rock composed of fine quartz crystals. The rock seen in Figure 7.75 is an example. The rock seen in Figure 7.75 is an example. Chert (the rock) is usually of biological origin, being the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor.Note quartz mosaic in chert region. Age. Early Carboniferous. Location. Carboniferous Limestone Skyes, Bowland, Yorkshire. Hand ...In thin section the chert is a heterogeneous mixture of finely crystalline quartz, later porosity fillings, and many fragments of plants. There is some evidence ...1. It is composed of calcite (CaCO3). · 2. Limestone of biological origin has shells and skeletons of marine animals and algae. · 3. Inorganic limestone is ...7 ม.ค. 2562 ... A chert is a sedimentary rock that occurs in nature as layered deposits, concretionary masses or nodules. It's a variety of chalcedony and ...Outcrop of Franciscan radiolarian chert in San Francisco, California Radiolarian chert outcrop near Cambria, California.Individual beds range from about 2 to 5 cm thick Radiolarite from the Alps.. Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the …Chert is a sedimentary rock in the class known as chemical sedimentary rocks. It is composed of microcrystalline quartz. Chemical Sedimentary Rocks: Group: Texture: Composition: Rock Name: Inorganic: Nonclastic: Microcrystalline quartz, SiO 2: Chert: Biochemical: Nonclastic: Microcrystalline quartz, SiO 2: Chert: Chert is very hard and …Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. They form from deposits that accumulate on the Earth's surface. Sedimentary rocks often have distinctive layering or bedding. Many of the picturesque views of the desert southwest show mesas and arches made of layered sedimentary rock. Common Sedimentary …
A fine-grained silica-rich rock occurring within sedimentary and volcanic rocks: Cryptocrystalline silica Composed of extremely fine (submicroscopic) silica .... Office of the university registrar
Chert is a chemically precipitated sedimentary rock, essentially monomineralic and composed of microcrystalline quartz and chalcedony with minor amounts of impurities such as clay minerals, silt, carbonate, pyrite and organic matter and, in some cases, opal (Folk 1980). Chert can be composed of authigenic silica due to precipitation …Outcrop of Franciscan radiolarian chert in San Francisco, California Radiolarian chert outcrop near Cambria, California.Individual beds range from about 2 to 5 cm thick Radiolarite from the Alps.. Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the …Rocks: Igneous, Metamorphic and Sedimentary Rocks hold the history of the earth and the materials that will be used to build its future. Igneous. Igneous Rocks: Photos, descriptions and facts about intrusive and extrusive igneous rocks. Andesite. Basalt. Dacite. Diabase. Diorite. Gabbro. Granite. ... Flint, Chert, Jasper. Flint, Chert, and Jasper are …Volcanic fragments: Fragmentation of volcanic rocks releases phenocrysts and groundmass clasts to the depositional setting.The composition of groundmass varies with rock type but consists mostly of glass or its alteration products (commonly zeolites, clays and chert), and small crystals of feldspar, quartz, ferromagnesian minerals, and …Sedimentary rocks make up only 5% (by volume) of the upper 10 miles of the crust, but about 75% of the outcrops on the continents. Two primary types of sedimentary rocks: ... Chert - a variety of cryptocrystalline (no crystal structure) silica; formed by the precipitation of silica from solution. Flint: a variety of chert which is dark owing to the presence of …But how about when the chert forms the greater part of the rock? ... Some of the very oldest sedimentary rocks, in greenstone terranes, are bedded cherts.Grey bedded chert specimen illustration. Sedimentary rock sample isolated on white background. เวกเตอร์. Landscape scenic view of desolate barren western desert ...OTHER SEDIMENTARY ROCKS: CHERT AND EVAPORITES 1. CHERT 1.1 Introduction 1.1.1 Chert is the general term for very fine-grained and nonporous sedimentary rocks that consist mostly or entirely of silica, in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The non-scientific …Shale) 7 Chemical No grain size gypsum Rock Gypsum 8 Clastic >2 mm rounded quartz, feldspar, and rock fragments Conglomerate 9 Chemical no grain size silica (quartz) Chert 10 Clastic 1/16 – 2 mm quartz, feldspar Sandstone 11 Clastic 1/16-2mm Quartz, feldspar Sandstone. Using the image above answer the following questions: a.The Rhynie chert, examined from float blocks, trench and cored material exhibits a wide range of macro-. textures (those large enough to be visible in hand specimen) and micro-textures (those clearly visible using. optical microscope techniques). Studying both, together with the biota the individual beds contain, can help.The form in which chert occurs is extremely varied, a consequence of the many different processes which lead to its formation in sedimentary rocks. The main ...Sedimentary rocks are types of rock that are formed by the deposition of material at the earth’s surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to ... Calcite, Dolomite Chert, Gypsum Anatase, Feldspar,Mica The siliciclastic …Left: A calcareous concretion exposed in Devonian-aged sedimentary rock at Watkins Glen State Park, New York. Left: A calcareous concretion in the PRI collections. ... Chert Nodules. Chert nodules are not concretions, but in Devonian rocks of central New York they can frequently have bizarre shapes that are similar to those of concretions ...Samples from the McMurray Lake chert have Al 2 O 3 /TiO 2 values ranging between nearly equal 19 and nearly equal 28, and REE patterns characterized by LREE enrichment, negative Eu anomalies, and slightly fractionated HREE patterns. These features, along with mean Th/Sc and Th/U values, indicate a source area dominated by …Sedimentary rock - Silica, Clastic, Chemical: Those siliceous rocks composed of an exceptionally high amount of crystalline siliceous material, mainly the mineral quartz (especially microcrystalline quartz and fibrous chalcedony) and amorphous opal, are most commonly known as chert. A wide variety of rock names are applied to cherty rocks reflecting their colour (flint is dark chert; jasper is ... 1 Chert is the general term for very fine-grained and nonporous sedimentary rocks that consist mostly or entirely of silica, in the form of either amorphous ...1.1.1 Chert is the general term for very fine-grained and nonporous sedimentary rocks that consist mostly or entirely of silica, in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The non-scientific equivalent term is flint. 1.1.2 Cherts are fairly easy to identify, ....