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Cadmoselite
Cadmoselite is a rare cadmium selenide mineral with chemical formula CdSe. Cadmoselite crystallizes in the Hexagonal (crystal system), hexagonal system and occurs as black to pale grey opaque crystals and grains.http://rruff.geo.arizona.edu/doclib/hom/cadmoselite.pdf Handbook of Mineralogyhttp://webmineral.com/data/Cadmoselite.shtml Webmineral data It was first described in 1957 for an occurrence in Tuva. The mineral occurs as interstitial grains in sandstone formed under Redox, reducing alkaline diagenesis, diagenetic conditions. References *Emsley, John. ''Nature's Building Blocks.'' Oxford, 2001. Cadmium minerals Selenide minerals Hexagonal minerals Minerals in space group 186 {{Mineral-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Selenide
Cadmium selenide is an inorganic compound with the formula Cadmium, CdSelenide, Se. It is a black to red-black solid that is classified as a II-VI semiconductor of the n-type semiconductor, n-type. Much of the current research on this compound is focused on its nanoparticles. Structure Three crystalline forms of CdSe are known which follow the structures of: Wurtzite (crystal structure), wurtzite (hexagonal), Cubic crystal system#Zincblende structure, sphalerite (cubic) and Cubic crystal system#Rock-salt structure, rock-salt (cubic). The sphalerite CdSe structure is unstable and converts to the wurtzite form upon moderate heating. The transition starts at about 130 °C, and at 700 °C it completes within a day. The rock-salt structure is only observed under high pressure. Production The production of cadmium selenide has been carried out in two different ways. The preparation of bulk crystalline CdSe is done by the High-Pressure Vertical Bridgman method or High-Pressur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmoselite
Cadmoselite is a rare cadmium selenide mineral with chemical formula CdSe. Cadmoselite crystallizes in the Hexagonal (crystal system), hexagonal system and occurs as black to pale grey opaque crystals and grains.http://rruff.geo.arizona.edu/doclib/hom/cadmoselite.pdf Handbook of Mineralogyhttp://webmineral.com/data/Cadmoselite.shtml Webmineral data It was first described in 1957 for an occurrence in Tuva. The mineral occurs as interstitial grains in sandstone formed under Redox, reducing alkaline diagenesis, diagenetic conditions. References *Emsley, John. ''Nature's Building Blocks.'' Oxford, 2001. Cadmium minerals Selenide minerals Hexagonal minerals Minerals in space group 186 {{Mineral-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ''plus'' (+) and ''minus'' (−) signs. These are limited to a single typographic line of symbols, which may include Subscript and superscript, subscripts and superscripts. A chemical formula is not a chemical nomenclature, chemical name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than chemical names and structural formulae. The simplest types of chemical formulae are called ''empirical formulae'', which use letters and numbers ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexagonal (crystal System)
In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal system and the rhombohedral lattice system are not equivalent (see section crystal systems below). In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz). The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal crystal system. There are 52 space groups associated with it, which are exactly those whose Bravais lattice is either hexagonal or rhombohedral. __TOC__ Lattice systems The hexagonal crystal family consists of two lattice systems: hexagonal and rhombohedral. Each lattice system consists of one Bravais l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuva
Tuva (; russian: Тува́) or Tyva ( tyv, Тыва), officially the Republic of Tuva (russian: Респу́блика Тыва́, r=Respublika Tyva, p=rʲɪˈspublʲɪkə tɨˈva; tyv, Тыва Республика, translit=Tyva Respublika ), is a federal subject of Russia (a republic, also defined in the Constitution of the Russian Federation as a state). The Tuvan Republic lies at the geographical center of Asia, in southern Siberia. The republic borders the Altai Republic, the Republic of Khakassia, Krasnoyarsk Krai, Irkutsk Oblast, and the Republic of Buryatia in Russia and Mongolia to the south. Tuva has a population of 307,930 ( 2010 census). Its capital is the city of Kyzyl. From 1921 to 1944, Tuva constituted a sovereign, independent, but partially recognized nation, acknowledged only by its neighbors the Soviet Union and Mongolia. It was known officially as Tannu Tuva until 1926 and thereafter as the Tuvan People's Republic. A majority of the population are ethni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkaline
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline, and less often, alkalescent, is commonly used in English language, English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the acid-base reaction theories#Arrhenius theory, Arrhenius definition of a base, and they are still among the most common bases. Etymology The word "alkali" is derived from Arabic ''al qalīy'' (or ''alkali''), meaning ''the calcined ashes'' (see calcination), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diagenesis
Diagenesis () 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 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 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, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Minerals
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled ''d'' or ''f'' electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate. Cadmium occurs as a minor component in most zinc ores and is a byproduct of zinc production. Cadmium was used for a long time as a corrosion-resistant plating on steel, and cadmium compounds are used as red, orange ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenide Minerals
Selenide minerals are those minerals that have the selenide anion as a main component. Selenides are similar to sulfides and often grouped with them. Examples include: * achavalite * athabascaite * clausthalite * ferroselite * penroseite * stilleite * tiemannite * umangite Umangite is a copper selenide mineral, Cu3 Se2, discovered in 1891. It occurs only in small grains or fine granular aggregates with other copper minerals of the sulfide group. It has a hardness of 3. It is blue-black to red-violet in color with ... References {{Mineral-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexagonal Minerals
In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A '' regular hexagon'' has Schläfli symbol and can also be constructed as a truncated equilateral triangle, t, which alternates two types of edges. A regular hexagon is defined as a hexagon that is both equilateral and equiangular. It is bicentric, meaning that it is both cyclic (has a circumscribed circle) and tangential (has an inscribed circle). The common length of the sides equals the radius of the circumscribed circle or circumcircle, which equals \tfrac times the apothem (radius of the inscribed circle). All internal angles are 120 degrees. A regular hexagon has six rotational symmetries (''rotational symmetry of order six'') and six reflection symmetries (''six lines of symmetry''), making up the dihedral group D6. The longest diagonals of a regular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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