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Cesanite
Cesanite is the end member of the apatite- wilkeite- ellestadite series that substitutes all of apatite's phosphate ions with sulfate ions and balances the difference in charge by replacing several calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ... ions with sodium ions. Currently very few sites bearing cesanite have been found and are limited to a geothermal field in Cesano (RM), Cesano, Italy from which its name is derived, Măgurici Cave in Romania, and in the San Salvador Island caves in the Bahamas. History Cesanite was first discovered in 1981 while the Italian National Electricity Board was doing exploratory drilling to examine a reservoir of heated brine to determine its potential as a geothermal energy source. When it was first found it was thought to be an apatite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfate Minerals
The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary minerals in the oxidizing zone of sulfide mineral deposits. The chromate and manganate minerals have a similar structure and are often included with the sulfates in mineral classification systems.Klein, Cornelis and Cornelius S. Hurlbut, 1985, ''Manual of Mineralogy,'' 20th ed., John Wiley and Sons, New York, pp. 347–354 . Sulfate minerals include: *Anhydrous sulfates ** Barite BaSO4 ** Celestite SrSO4 ** Anglesite PbSO4 ** Anhydrite CaSO4 ** Hanksite Na22K(SO4)9(CO3)2Cl *Hydroxide and hydrous sulfates ** Gypsum CaSO4·2H2O **Chalcanthite CuSO4·5H2O ** Kieserite MgSO4·H2O ** Starkeyite MgSO4·4H2O ** Hexahydrite MgSO4·6H2O ** Epsomite MgSO4·7H2O ** Meridianiite MgSO4·11H2O **Melanterite FeSO4·7H2O ** Antlerite Cu3SO4(OH)4 ** ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bahamas
The Bahamas, officially the Commonwealth of The Bahamas, is an archipelagic and island country within the Lucayan Archipelago of the Atlantic Ocean. It contains 97 per cent of the archipelago's land area and 88 per cent of its population. It comprises more than 3,000 islands, cays and islets in the Atlantic Ocean, and is located north of Cuba and north-west of the island of Hispaniola (split between the Dominican Republic and Haiti) and the Turks and Caicos Islands, southeast of the U.S. state of Florida and east of the Florida Keys. The capital and largest city is Nassau on the island of New Providence. The Royal Bahamas Defence Force describes the Bahamas' territory as encompassing of ocean space. The Bahama islands were inhabited by the Arawak and Lucayans, a branch of the Arawakan- speaking Taíno, for many centuries. Christopher Columbus was the first European to see the islands, making his first landfall in the "New World" in 1492 when he landed on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in a material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice. The lengths of principal axes/edges, of the unit cell and angles between them are lattice constants, also called ''lattice parameters'' or ''cell parameters''. The symmetry properties of a crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Analog
A structural analog, also known as a chemical analog or simply an analog, is a chemical compound, compound having a chemical structure, structure similar to that of another compound, but differing from it in respect to a certain component. It can differ in one or more atoms, functional groups, or substructures, which are replaced with other atoms, groups, or substructures. A structural analog can be imagined to be formed, at least theoretically, from the other compound. Structural analogs are often isoelectronicity, isoelectronic. Despite a high chemical similarity, structural analogs are not necessarily functional analog (chemistry), functional analogs and can have very different physical, chemical, biochemical, or pharmacological properties. In drug discovery, either a large series of structural analogs of an initial lead compound are created and tested as part of a structure–activity relationship study or a database is virtual screening, screened for structural analogs of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that leave it unchanged. In three dimensions, space groups are classified into 219 distinct types, or 230 types if chiral copies are considered distinct. Space groups are discrete cocompact groups of isometries of an oriented Euclidean space in any number of dimensions. In dimensions other than 3, they are sometimes called Bieberbach groups. In crystallography, space groups are also called the crystallographic or Fedorov groups, and represent a description of the symmetry of the crystal. A definitive source regarding 3-dimensional space groups is the ''International Tables for Crystallography'' . History Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahedra
In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tetrahedron is the simplest of all the ordinary convex polytope, convex polyhedra. The tetrahedron is the three-dimensional case of the more general concept of a Euclidean geometry, Euclidean simplex, and may thus also be called a 3-simplex. The tetrahedron is one kind of pyramid (geometry), pyramid, which is a polyhedron with a flat polygon base and triangular faces connecting the base to a common point. In the case of a tetrahedron, the base is a triangle (any of the four faces can be considered the base), so a tetrahedron is also known as a "triangular pyramid". Like all convex polyhedra, a tetrahedron can be folded from a single sheet of paper. It has two such net (polyhedron), nets. For any tetrahedron there exists a sphere (called th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bond Length
In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between atoms of fixed types, relatively independent of the rest of the molecule. Explanation Bond length is related to bond order: when more electrons participate in bond formation the bond is shorter. Bond length is also inversely related to bond strength and the bond dissociation energy: all other factors being equal, a stronger bond will be shorter. In a bond between two identical atoms, half the bond distance is equal to the covalent radius. Bond lengths are measured in the solid phase by means of X-ray diffraction, or approximated in the gas phase by microwave spectroscopy. A bond between a given pair of atoms may vary between different molecules. For example, the carbon to hydrogen bonds in methane are different from those in methyl chlori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its atomic nucleus, nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules. Some elements form Homonuclear molecule, molecules of atoms of said element only: e.g. atoms of hydrogen (H) form Diatomic molecule, diatomic molecules (H). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unit Cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector in a normed vector space is a Vector (mathematics and physics), vector (often a vector (geometry), spatial vector) of Norm (mathematics), length 1. A unit vector is often denoted by a lowercase letter with a circumfle ..., for example) does not necessarily have unit size, or even a particular size at all. Rather, the primitive cell is the closest analogy to a unit vector, since it has a determined size for a given lattice and is the basic building block from which larger cells are constructed. The concept is used particularly in describing crystal structure in two and three dimensions, though it makes sense in all dimensions. A lattice can be characterized by the geometry of its unit cell, which is a section of the tiling (a parallelogra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxylapatite
Hydroxyapatite ( IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the formula , often written to denote that the crystal unit cell comprises two entities. It is the hydroxyl endmember of the complex apatite group. The ion can be replaced by fluoride or chloride, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis. Up to 50% by volume and 70% by weight of human bone is a modified form of hydroxyapatite, known as bone mineral. Carbonated calcium-deficient hydroxyapatite is the main mineral of which dental enamel and dentin are composed. Hydroxyapatite crystals are also found in pathological calcifications such as those found in breast tumors, as well as calcifications within the pineal gland (and ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotypic
Isostructural chemical compounds have similar chemical structures. " Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous substances crystallise in the same space group and have the same unit cell dimensions. The IUCR definition used by crystallographers is: Examples include: *I- Gold(I) bromide is isostructural with gold(I) chloride *Borazine is isostructural with benzene * Indium(I) bromide is isostructural with β- thallium(I) iodide and has a distorted rock salt structure. Many minerals are isostructural when they differ only in the nature of a cation. Compounds which are isoelectronic usually have similar chemical structures. For example, methane, CH4, and the ammonium ion, NH4+, are isoelectric and are isostructural as both have a tetrahedral structure. The C-H and N-H bond lengths are different and crystal structures are completely different bec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geothermal Energy
Geothermal energy is thermal energy extracted from the crust (geology), crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for millennia. Geothermal heating, using water from hot springs, for example, has been used for bathing since Paleolithic times and for space heating since Roman times. Geothermal power (generation of electricity from geothermal energy), has been used since the 20th century. Unlike wind and solar energy, geothermal plants produce power at a constant rate, without regard to weather conditions. Geothermal resources are theoretically more than adequate to supply humanity's energy needs. Most extraction occurs in areas near tectonic plate boundaries. The cost of generating geothermal power decreased by 25% during the 1980s and 1990s. Technological advances continued to reduce costs and thereby expand the amount of viable resources. In 2021, the US ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
