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Authigenic
Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed. Such deposits are described as authigenic. Authigenic sedimentary Mineral, minerals form during or after sedimentation by Precipitation (chemistry), precipitation or Recrystallization (geology), recrystallization as opposed to detrital minerals, which are weathered by water or wind and transported to the depositional location. Authigenic sediments are the main constituents of deep sea sedimentation, compared to shallow waters or land where detrital sediments are more common. Authigenesis process The authigenesis process is driven by particles of sediment that are not in thermodynamic equilibrium with the conditions surrounding it. This often occurs in the ocean where changing conditions due to biological processes is common. In water, changing oxygen content or changing saturation causes Precipitation (chemistry), precipitation of minerals into the sediments, chang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glauconite
Glauconite is an iron potassium phyllosilicate ( mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () meaning 'bluish green', referring to the common blue-green color of the mineral; its sheen ( mica glimmer) and blue-green color. Its color ranges from olive green, black green to bluish green, and yellowish on exposed surfaces due to oxidation. In the Mohs scale it has a hardness of 2, roughly the same as gypsum. The relative specific gravity range is 2.4–2.95. It is normally found as dark green rounded concretions with the dimensions of a sand grain. It can be confused with chlorite (also of green color) or with a clay mineral. Glauconite has the chemical formula . Glauconite particles are one of the main components of greensand, glauconitic siltstone and glauconitic sandstone. Glauconite has been called a marl in an old and br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petrology
Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together because both make heavy use of chemistry, chemical methods, and phase diagrams. Sedimentary petrology is commonly taught together with stratigraphy because it deals with the processes that form sedimentary rock. Modern sedimentary petrology is making increasing use of chemistry. Background Lithology was once approximately synonymous with petrography, but in current usage, lithology focuses on macroscopic hand-sample or outcrop-scale description of rocks while petrography is the speciality that deals with microscopic details. In the petroleum industry, lithology, or more specifically mud logging, is the graphic representation of geological formations being drilled through and drawn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neomorphism
Neomorphism refers to the wet metamorphic process in which diagenetic alterations systematically transform minerals into either polymorphs or crystalline structures that are structurally identical to the rock(s) from which they developed. Coined by the late Robert L. Folk, ''neomorphism'' encompasses the functions of both recrystallization and inversion, which are geological processes that deal primarily with rock reformation. The neomorphic process, as it relates to geology and petrography, is one of the many major processes that sustain both carbonate minerals and limestone. Neomorphism is largely held accountable for the metastability of aragonite and magnesium-rich calcite, and when conditions permit, neomorphic reactions and interactions can result in texture loss and/or feature deformation of affected rock formations. Types of neomorphism Recrystallization The term "recrystallization" broadly refers to the many metamorphic processes that change the size and/or shape of c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrite
The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of ''fool's gold''. The color has also led to the nicknames ''brass'', ''brazzle'', and ''brazil'', primarily used to refer to pyrite found in coal. The name ''pyrite'' is derived from the Greek (), 'stone or mineral which strikes fire', in turn from (), 'fire'. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what is now called pyrite. By Georgius Agricola's time, , the term had become a generic term for all of the sulfide minerals. Pyrite is usually found associated with other sulfides or oxides in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. Examples include fused quartz, fumed silica, opal, and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored. Silicon dioxide is a common fundamental constituent of glass. Structure In the majority of silicon dioxides, the silicon atom shows Tetrahedral molecular geometry, tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siderite
Siderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly substitute for the iron, resulting in the siderite-smithsonite, siderite-magnesite, and siderite-rhodochrosite solid solution series. Siderite has Mohs hardness of 3.75 to 4.25, a specific gravity of 3.96, a white streak and a vitreous or pearly luster. Siderite is antiferromagnetic below its Néel temperature of that can assist in its identification. It crystallizes in the trigonal crystal system; crystals are rhombohedral in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black, the latter being due to the presence of manganese. Siderite is commonly found in hydrothermal veins, and is associated with barite, fluorite, galena, and others. It is also a common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chamosite
Chamosite is the Fe2+end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low-to-moderate-grade metamorphosed iron deposits, as gray or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal alteration of pyroxenes, amphiboles and biotite in igneous rock. The composition of chlorite is often related to that of the original igneous mineral, so that more Fe-rich chlorites are commonly found as replacements of the Fe-rich ferromagnesian minerals (Deer et al., 1992). History In 1820, Pierre Bertier, a mineralogist and mining engineer from Nemours, France, discovered chamosite. The new mineral was found in an area of low-to-moderate-grade metamorphosed iron deposits. Early samples of chamosite (which is a chlorite) stirred some controversy after they were found to possess the structure of kaolin rather than chlorite; however, further research proved that chamosite was found in nature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limonite
Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as , although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mining, mined for the production of iron since at least 400 BC. Names Limonite is named for the Ancient Greek word ( ), meaning "wet meadow", or ( ), meaning "marshy lake", as an allusion to its occurrence as in meadows and marshes. In its brown form, it is sometimes called brown hematite or brown iron ore. Characteristics Limonite is relatively density, dense with a specific gravity varying from 2.7 to 4.3.Northrop, Stuart A. (1959) "Limonite" ''Minerals of New Mexico'' (revised edition) University of New Mexico Press, Albuquerque, New Mexico, pp. 329–333, It is usually medium to dark yellowish brown in color. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hematite
Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . It has the same crystal structure as corundum () and ilmenite (). With this it forms a complete solid solution at temperatures above . Hematite occurs naturally in black to steel or silver-gray, brown to reddish-brown, or red colors. It is mined as an important ore mineral of iron. It is electrically conductive. Hematite varieties include ''kidney ore'', ''martite'' ( pseudomorphs after magnetite), ''iron rose'' and ''specularite'' ( specular hematite). While these forms vary, they all have a rust-red streak. Hematite is not only harder than pure iron, but also much more brittle. The term ''kidney ore'' may be broadly used to describe botryoidal, mammillary, or reniform hematite. Maghemite is a polymorph of hematite (γ-) with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide. Clays develop plasticity (physics), plasticity when wet but can be hardened through Pottery#Firing, firing. Clay is the longest-known ceramic material. Prehistoric humans discovered the useful properties of clay and used it for making pottery. Some of the earliest pottery shards have been radiocarbon dating, dated to around 14,000 BCE, and Clay tablet, clay tablets were the first known writing medium. Clay is used in many modern industrial processes, such as paper making, cement production, and chemical filtration, filtering. Between one-half and two-thirds of the world's population live or work in buildings made with clay, often baked into brick, as an essenti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of the three most common Endmember (mineralogy), endmembers is written as Calcium, Ca10(Phosphate, PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6F2 and Ca10(PO4)6Cl2. The mineral was named apatite by the German geologist Abraham Gottlob Werner in 1786, although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German mineralogist Karl Friedrich August Rammelsberg. Apatite is often mistaken for other minerals. This tendency is reflected in the mineral's name, which is derived from the Greek word ἀπατάω (apatáō), which means ''to deceive''. Geology Apatite is very common as an accessory mineral in igneous and metamorphic roc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
