Chert chemical composition

1.1 Formation. Chert forms when microcrystals of silicon dioxide grow within soft sediments that become limestone or chalk. The chert formation can be either of chemical or biological origin. 1.2 Composition. 1.2.1 Mineral Content. Quartz, Silicon. 1.2.2 Compound Content. Silicon Dioxide. 1.3 Transformation.

Chert chemical composition. Flint is a widely used material in the Stone Age because of its physical characteristics, which makes the material suitable for obtaining tools with sharp working edges. Chert, flint, chalcedony, agate and jasper in composition and several other physical characteristics are very similar. Therefore in archaeology most often they are determined simplified and are not distinguished, but described ...

Chert is very hard and compact. A number of other rock names are applied to varieties of chert. Flint is dark-colored chert that contains organic matter to contribute the dark color. Jasper is a red variety, deriving its color from iron oxide. Chert occurs in banded forms that are commonly called agate.

This study will show that a classic geology type geochemical XRF technique, using a modified non-destructive method (Gauthier and Burke, 2011), is well suited, firstly for the determination of the major and trace element composition of chert, and secondly for chert fingerprinting when the more robust and representative chemical elements are …Chert. Chert is a sedimentary rock consisting almost entirely of silica (SiO 2 ), and can form in a variety of ways. Biochemical chert is formed when the siliceous skeletons of marine plankton are dissolved during diagenesis, with silica being precipitated from the resulting solution. Replacement chert forms when other material is replaced by ... 4 sty 2021 ... ... Chert, South Africa which indicate that they possess significantly different chemical compositions. ... composition of organic molecules over ...Siltstone, hardened sedimentary rock that is composed primarily of angular silt-sized particles (0.0039 to 0.063 mm [0.00015 to 0.0025 inch] in diameter) and is not laminated or easily split into thin layers. Siltstones, which are hard and durable, occur in thin layers rarely thick enough to beChert and associated host sediments from Monterey Formation and Deep Sea Drilling Project (DSDP) sequences were analyzed in order to assess chemical behavior during diagenesis of biogenic sediments. The primary compositional contrast between chert and host sediment is a greater absolute SiO 2 concentration in chert, often with final SiO …Chert, also known as flint, is a silica-rich sedimentary rock. Chert is very hard and its conchoidal fractures can leave sharp edges which do not dull easily.

Chemical Formula: CaCO3 : Composition: Molecular Weight = 100.09 gm Calcium 40.04 % Ca 56.03 % CaO Carbon 12.00 % C 43.97 % CO 2 Oxygen ... Parakutnohorite - intermediate composition between calcite and rhodochrosite : Travertine : Calcite Image: Images: Calcite Quartz.Chemical Composition: CaMg(CO3)2 - Calcium Magnesium Carbonate. Iron may substitute for some of the magnesium. Color: Transparent to translucent crystals are typically colorless, white, gray or pink, but if iron impurities are present can be red, brown or even black. In massive form, dolomite is typically buff, gray, or white. CleavageChert - Compact form of Chalcedony typically found as nodule s in sedimentary rock s, usually with an off-white, gray, or cream color. Although technically Chert is classified as a rock due to its composition of other mineral impurities , it most often is regarded as a variety of Chalcedony.Dolomite's chemical formula is CaMg (CO 3) 2. Cherts. Chert (varieties of which are flint, agate, and jasper) is a hard, glassy sedimentary rock composed of silica that precipitated from water. Chert nodules, also known as geodes, are commonly found in limestones and less so in clastic sedimentary rocks. They form in pockets or voids that might ...Radiolarian skeletons in siliceous sediments are made from biogenic opal (Opal-A), while in mature chert sequences quartz is the main silica phase. Biogenic opal is an amorphous silica phase with a chemical composition of SiO 2 ⋅ n H 2 O; the water content may vary widely from 3 to 21% but is usually between 6 and 10% (e.g., Day and …

Rock Composition. Flint is composed of microscopic crystals of the mineral quartz (SiO2). Flint is quite similar to chert in many ways. The chert found in chalk was originally called flint. Flint is usually made up of petrified (fossilized) remains of siliceous ooze, the biological remains of marine organisms like diatoms, silicoflagellates ...Physical and chemical properties. The crystallographic structures of the silica minerals, except stishovite, are three-dimensional arrays of linked tetrahedrons, each consisting of a silicon atom coordinated by four oxygen atoms. The tetrahedrons are usually quite regular, and the silicon-oxygen bond distances are 1.61 ± 0.02 Å.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. …Mar 1, 2020 · Radiolarian skeletons in siliceous sediments are made from biogenic opal (Opal-A), while in mature chert sequences quartz is the main silica phase. Biogenic opal is an amorphous silica phase with a chemical composition of SiO 2 ⋅ n H 2 O; the water content may vary widely from 3 to 21% but is usually between 6 and 10% (e.g., Day and Jones, 2008).

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A new classification scheme for non-detrital siliceous rocks is proposed, facts and problems coneerning the origin of cherts are discussed, and a new genetic model is presented. The relationship between opal-and quartz-silica phases is discussed, and it is suggested that most of the quartz cherts originated from opaline precursors. The diagenetic opal/quartz transformation is interpretated as ...Iron ore from Kryvyi Rih, Ukraine.. Iron-rich sedimentary rocks are sedimentary rocks which contain 15 wt.% or more iron.However, most sedimentary rocks contain iron in varying degrees. The majority of these rocks were deposited during specific geologic time periods: The Precambrian (3800 to 539 million years ago), the early Paleozoic (539 to 419 million …Obsidian was used to make knives, arrowheads, spear points, scrapers, and many other weapons and tools. Once these discoveries were made, obsidian quickly became the raw material of preference for producing almost any sharp object. The easy-to-recognize rock became one of the first targets of organized "mining."Pictures Jasper is a hematite-bearing variety. Hematite is an iron oxide that is the most widespread source of red color in minerals and rocks. The sample is from the Løkken ophiolite in Norway. It is associated with …In this lab, we will look at three types of clastic rocks (Figure 10.1, Table 10.1), conglomerate, sandstone, and shale. Conglomerate is an immature sedimentary rock (rock that has been transported a short distance) that is a poorly sorted mixture of clay, sand, and rounded pebbles. The mineralogy of the sand and pebbles (also called clasts ...The bond between sodium (na) and Chlorine (Cl) to form halite (salt) is a (n) bond. ionic. The bond between two hydrogen atoms (a covalent bond) is based on the force of attraction between _______. protons and electrons in the same atom. Atoms that have an electrical charge due to a gain or loss of electrons are called.

Despite appearance, all forms of chert have the same basic composition. It is a hard, brittle sedimentary rock composed of finely crystalline quartz and its chemical base is silica (SiO 2). The presence of impurities gives the stone colors other than white.Water-lain chemical sediments are the most important archives for paleo-temperature reconstruction. The most common chemical sediments from the Archean eon (4.0–2.5 Ga) are silica cherts, with the oldest occurrences dating back to 3.8 Ga (Nutman et al., 1997).An example of a massive chert rock is the 3.46 Ga old Marble Bar chert from …Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. … See moreArtifacts of chert excavated in an archaeological context are invaluable to archaeologists; they are often the only surviving source of information about prehistoric cultures. This useful reference synthesizes the available information on chert and its properties, examining its origins, chemical composition, appearance, mechanical attributes ...A possible mechanism of rhythmic alternation of bedded cherts revealed by their chemical composition. J Earth Planet Sci, Nagoya Univ, 1998, 45: 29–39 ... et al. Rare earth, major, and trace element composition of Monterey and DSDP chert and associated host sediment: Assessing the influence of chemical fractionation during …Abstract. Research of chert chemical composition in geoarchaeology is mainly linked with the raw material sourcing of artefacts. However, the natural diversity and heterogeneity of chert make such ...Two alternative interpretations are as follows: (i) Archean surface temperatures were similar to today’s because the oxygen isotope composition of seawater, δ 18 O seawater, increased by ~15‰ since 3.5 Ga ago (229, 230). (ii) Older cherts and carbonates have nonprimary δ 18 O from high alteration temperatures or hydrothermal fluids (55, 231).The supposed restrictions of secondary chert formation to near-shore positions could prove to be a very important tool in palaeogeographic reconstructions especially for sedimentary sequences now found in deeper water environments. ... SHEPPARD, R.A., A.J. GUDE & GRIFFIN, J.J. (1970): Chemical composition and physical properties of phillipsite ...Aragonite is a polymorph of calcite, a mineral that has the same chemical composition as calcite, but has a slightly different crystal structure. For most purposes aragonite and calcite can be considered to be the same mineral. In its crystal form, aragonite tends to have needlelike crystals and lacks calcite’s rhombohedral cleavage.Siltstone, hardened sedimentary rock that is composed primarily of angular silt-sized particles (0.0039 to 0.063 mm [0.00015 to 0.0025 inch] in diameter) and is not laminated or easily split into thin layers. Siltstones, which are hard and durable, occur in thin layers rarely thick enough to beThe composition of the Hadean atmosphere is obscured by a lack of well-preserved rocks, but analysis of zircons—crystals of zirconium silicate (ZrSiO 4)—suggests that continents, oceans, and perhaps life all originated in the Hadean ().Zircons are tiny (<0.5 mm) durable pieces of continental crust.

Quartz is a mineral composed of silicon and oxygen, with a chemical composition of SiO 2. It is the most abundant mineral in Earth's crust and is resistant to both chemical and physical weathering. When rocks weather away, the residual material usually contains quartz. This is why the sand at most of the world's beaches is quartz.

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 ...A. Chemical sedimentary rocks are crystalline in texture. B. Gypsum and halite are evaporite minerals. C. Both chert and limestone may have either chemical or biochemical origin. D. Dolostone and limestone are polymorphs—they have the same chemical composition. D. Dolostone and limestone are polymorphs—they have the same …Chert is by far the most abundant lithic fragment preserved in the Tantalus formation, making up 77% of the framework of the conglomerate and 56% of the sandstone. This is in marked contrast with the underlying Tanglefoot formation, in which only 16% of the framework grains in conglomerates and 5.5% in sandstones consist of chert.Nov 28, 2020 · A chert nodule is a small and irregularly rounded knot, lump, or mass in surrounding sedimentary rock. Having a contrasting chemical composition will separate the chert sediment contents from the limestone sediment contents, or host sediment. Differences Between Chert and Flint. The differences between Chert vs Flint are not too many. The term chert is applied here to all fine-grained siliceous sediments and sedimentary rocks of chemical, biochemical, and organic origin. ... chert deposits of ...Nov 28, 2020 · A chert nodule is a small and irregularly rounded knot, lump, or mass in surrounding sedimentary rock. Having a contrasting chemical composition will separate the chert sediment contents from the limestone sediment contents, or host sediment. Differences Between Chert and Flint. The differences between Chert vs Flint are not too many. 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 ... Chemical Formula: SiO2 : Composition: Molecular Weight = 60.08 gm Silicon 46.74 % Si 100.00 % SiO 2 ... Chert - cryptocrystalline quartz : Chrysoprase - apple green chalcedony : Citrine - yellow : Flint - microcrystalline quartz : Hornstone - flint

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Chert’s abrasive qualities make it useful as a polishing compound for metals, glass, and plastics. It serves as an additive in paints, tiles, and various chemical products. Silica derived from chert and flint is an essential raw material for manufacturing glass, ceramics, silicon metal, and silicon chemicals.Significance. Throughout Earth history, chemical sediments show an enigmatic increase in their 18 O/ 16 O isotope ratios (δ 18 O) of ~15‰. This has been interpreted as evidence for either very hot (>70 °C) or very 18 O-depleted early oceans. But both of these scenarios are hard to reconcile with other geological and geochemical evidence.The mean concentrations of oxides and elements in the Rex Chert and the cherty shale member are dominated by SiO2, which averages 94.6%. Organic-carbon contents are generally very low in the chert, but are up to 1.8 wt. % in cherty shale member samples and up to 3.3% in samples from the transition between the Meade Peak and Rex Chert.1.1 Formation. Chert forms when microcrystals of silicon dioxide grow within soft sediments that become limestone or chalk. The chert formation can be either of chemical or biological origin. 1.2 Composition. 1.2.1 Mineral Content. Quartz, Silicon. 1.2.2 Compound Content. Silicon Dioxide. 1.3 Transformation. The chemical composition of perfume is generally made up of two components: a base substance and various scented oils. Bases are usually made of a mixture of water (H2O) and ethyl alcohol (C2H6O), while the chemical composition of the oils ...Chert is a microcrystalline or cryptocrystalline sedimentary rock composed mainly of silica (silicon dioxide) ... Chemical Inertness: Chemically inert and ...@article{osti_886869, title = {Chemical controls on the Opal-A to Opal-CT Transformation}, author = {Kastner, M and Keene, J B}, abstractNote = {Since early Paleozoic the major mechanisms of silica precipitation at ordinary temperatures and pressures is biochemical. other mechanisms are: adsorption, organo-silicon complexing, evaporation or cooling of …Chert and flint, very fine-grained quartz (q.v.), a silica mineral with minor impurities. Several varieties are included under the general …The problems with chert come in its origin; it’s another one of those rocks whose origin we have a hard time observing directly. The relative importance of nodular chert and bedded chert has changed through geologic time: bedded chert is much more common in the Precambrian, and nodular chert is more common in the Phanerozoic. 1.2 TerminologyApr 23, 2023 · 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. The mean concentrations of oxides and elements in the Rex Chert and the cherty shale member are dominated by SiO2, which averages 94.6%. Organic-carbon contents are generally very low in the chert, but are up to 1.8 wt. % in cherty shale member samples and up to 3.3% in samples from the transition between the Meade Peak and Rex Chert.Dust storms are most likely to deposit windblown silt, commonly called ________. dunes desert pavement blowout loess. Deflation may lead to ________. till meanders blowouts drumlins. Study Ch. 1 - 4 Test GEL111 Earth Science flashcards. Create flashcards for FREE and quiz yourself with an interactive flipper. ….

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 ...Siltstone, hardened sedimentary rock that is composed primarily of angular silt-sized particles (0.0039 to 0.063 mm [0.00015 to 0.0025 inch] in diameter) and is not laminated or easily split into thin layers. Siltstones, which are hard and durable, occur in thin layers rarely thick enough to beApr 23, 2023 · 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. The grains of chert, mudrock, limesone, polycrystalline quartz, and volcanic rocks are also quite common.Clasts of detrital muscovite, biotite and chert occour in accossory amount.. Deep-water lifeless and bath body fossils, pelagic fauna and flora, and re-transferred shallow – waterrorganic remains are all found in wacke sandstone …During the Upper Ordovician–Lower Silurian, chert was widely distributed in the Zhongbao Formation in the eastern part of the North Qilian Orogen. The origin and the tectonic setting of these chert were largely unknown. ... The chemical composition of subducting sediment and its consequences for the crust and mantle. Chemical Geology 145, 325 ...... Chert is exposed and concentrated together to form a rich area. The name of [1] is derived from the unknown meaning of German quarz. Chemical composition: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 ... Chert chemical composition, Porcellanite is the term used to describe a porous siliceous sedimentary rock with a dull or matte luster similar to unglazed porcelain, whereas chert is the ..., Because a cow’s stomach includes four different chambers with their own chemical processes and biological functions, the chemical composition of cow dung includes a variety of different substances., Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, [1] chunks, and smaller grains of rock broken off other rocks by physical weathering. [2] Geologists use the term clastic to refer to sedimentary rocks and particles in sediment transport, whether in suspension or ..., Only in the first case does the chemical and isotopic composition of chert reflect the chemistry and temperature of Archean seawater. Chert is very resistant to surface weathering and associated chemical alteration. Therefore, chert is often considered to be the ideal agent for the preservation of very ancient and potentially extraterrestrial ..., a significant amount of chert waste in the quarries (up to 19 million tons) and, as a consequence, to the non-optimal use of natural, economical materials and the area of open pits (Figure 3d). This paper deals with the wide study of mechanical, physical properties and the chemical composition of chert gravels., Water-lain chemical sediments are the most important archives for paleo-temperature reconstruction. The most common chemical sediments from the Archean eon (4.0–2.5 Ga) are silica cherts, with the oldest occurrences dating back to 3.8 Ga (Nutman et al., 1997).An example of a massive chert rock is the 3.46 Ga old Marble Bar chert from …, Chert can be classified as either a chemical or a biogenic sedimentary rock, depending on how it forms. When chert forms through silica precipitating out of groundwater and solidifying, it is ‘chemical’. However, when it forms from the collection and solidification of microscopic silica remnants of living things it is ‘biogenic’., We present bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions, of rocks collected from three measured outcrop sections of the Rex Chert Member of the Phosphoria Formation in southeast Idaho. The three measured sec- tions were chosen from 10 outcrops of Rex Chert that were …, Question: Match each type of chemical sedimentary rocks with its composition. Chert (siliceous chemical sedimentary rocks) A. Carbonate minerals like ..., Dalmation jasper is the name for a white-yellowish stone with black spots. It’s igneous rock composed of arfvedsonite, albite and quartz and thus not jasper or chalcedony. Chalcedony is a broad term to describe a microcrystalline form of silica. Agate is any type of chalcedony which is translucent, while jasper is any type of chalcedony which ..., The other concern is that certain cherts undergo an alkali-silica reaction with high-alkali cements. This reaction leads to cracking and expansion of concrete and ultimately to failure of the material. Return to Minerals Database. Chert, also known as flint, is a silica-rich sedimentary rock. Chert is very hard and its conchoidal fractures can ... , Marine chemical sediments and altered oceanic crust preserve a geochemical record of these histories. Marine chemical sediments, for example, exhibit an increase in their 18O/16O ratio through time., Two alternative interpretations are as follows: (i) Archean surface temperatures were similar to today’s because the oxygen isotope composition of seawater, δ 18 O seawater, increased by ~15‰ since 3.5 Ga ago (229, 230). (ii) Older cherts and carbonates have nonprimary δ 18 O from high alteration temperatures or hydrothermal fluids (55, 231)., In this lab, we will look at three types of clastic rocks (Figure 10.1, Table 10.1), conglomerate, sandstone, and shale. Conglomerate is an immature sedimentary rock (rock that has been transported a short distance) that is a poorly sorted mixture of clay, sand, and rounded pebbles. The mineralogy of the sand and pebbles (also called clasts ..., Chert formed in this manner is a chemical sedimentary rock. Diatoms are microscopic, single-celled algae that live in marine or fresh water. They produce hard parts made of silicon dioxide. NASA Image. ... What is Chert's Composition? Chert is a microcrystalline silicon dioxide (SiO 2). As chert nodules or concretions grow within a sediment ..., 6 mar 2013 ... chertification is a diagenetic process that converts carbonate sediments into chert. ... They form siliceous Rocks that can arguably be chemical ..., It has the same chemical composition of quartz, bearing the chemical formula SiO2, however it forms in the monoclinic system as opposed to the hexagonal system of quartz. ... Chert Chert fits into the category of jasper for it forms from sedimentary processes where silica-rich solution precipitate through the sediment and solidify it into a ..., 2.1 billion year old rock from North America showing banded iron formation, displayed in Dresden, Saxony, Germany. Banded iron formations (BIFs; also called banded ironstone formations) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert.They can be up to several hundred meters in thickness and …, Nov 28, 2022 · Rock Composition. Flint is composed of microscopic crystals of the mineral quartz (SiO2). Flint is quite similar to chert in many ways. The chert found in chalk was originally called flint. Flint is usually made up of petrified (fossilized) remains of siliceous ooze, the biological remains of marine organisms like diatoms, silicoflagellates ... , Chert is a broad term for chemically precipitated sedimentary rocks made up of microcrystalline silica. Most charts are nearly pure silica with up to 5% other minerals like calcite, dolomite, clay minerals, hematite, and organic matter. Some cherts may have up to 99% silica, while others have 65% silica content., Chemical Composition: CaMg(CO3)2 - Calcium Magnesium Carbonate. Iron may substitute for some of the magnesium. Color: Transparent to translucent crystals are typically colorless, white, gray or pink, but if iron impurities are present can be red, brown or even black. In massive form, dolomite is typically buff, gray, or white. Cleavage, 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., Dolomite's chemical formula is CaMg (CO 3) 2. Cherts. Chert (varieties of which are flint, agate, and jasper) is a hard, glassy sedimentary rock composed of silica that precipitated from water. Chert nodules, also known as geodes, are commonly found in limestones and less so in clastic sedimentary rocks. They form in pockets or voids that might ..., a significant amount of chert waste in the quarries (up to 19 million tons) and, as a consequence, to the non-optimal use of natural, economical materials and the area of open pits (Figure 3d). This paper deals with the wide study of mechanical, physical properties and the chemical composition of chert gravels. , This study will show that a classic geology type geochemical XRF technique, using a modified non-destructive method (Gauthier and Burke, 2011), is well suited, firstly for the determination of the major and trace element composition of chert, and secondly for chert fingerprinting when the more robust and representative chemical elements are …, Chert - Compact form of Chalcedony typically found as nodule s in sedimentary rock s, usually with an off-white, gray, or cream color. Although technically Chert is classified as a rock due to its composition of other mineral impurities , it most often is regarded as a variety of Chalcedony., Chert and flint, very fine-grained quartz (q.v.), a silica mineral with minor impurities. Several varieties are included under the general …, Porcellanite is the term used to describe a porous siliceous sedimentary rock with a dull or matte luster similar to unglazed porcelain, whereas chert is the ..., Chalk is calcium carbonate and has the same chemical composition as limestone, marble, ground calcium carbonate and precipitated calcium carbonate. Chalk, like the other types of calcium carbonate, is in the form of calcite, which is a crys..., 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. The most usual colors a chert can take are gray, grayish brown, brown, light green, and rusty red. ... Rock Composition. Chert is mostly composed of microcrystalline ..., 7.5.2.3 Chert; 7.5.2.4 Other Chemical Sedimentary Rocks; Chemical sedimentary rocks are formed by precipitation of minerals from water or by alteration of already existing material in place. The most common of these rocks include evaporites, chert, and some varieties of carbonate rocks (limestones and dolostones). In contrast with clastic ..., Chemical Composition. Chalcedony is a mineral that is formed from silica gels at shallow temperatures. The silica is emancipated from igneous and sedimentary rocks, and they end up losing all the silica, for example, basalt. Chert is a sedimentary rock with refined grains which is made of microcrystalline quartz, which is in the form of silicon ..., Triple oxygen isotope data. The triple oxygen isotope composition of the studied cherts is listed in Table 2. The Archean cherts have δ 18 Ο values between 14 and 19‰ and corresponding Δ′ 17 O values of −0.10 to −0.06‰. The mean δ 18 Ο values for the bedded cherts (17.1 ± 1.0‰, 95% confidence level) are slightly higher than ...