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Cupalite
Cupalite is a rare mineral which is mostly composed of copper and aluminium, but might contain up to several percent of zinc or iron; its chemical structure is therefore described by an approximate formula or . It was discovered in 1985 in Placer deposit, placers derived from Serpentine group, serpentine, in association with another rare mineral khatyrkite (CuAl2). Both minerals are thus far restricted to the area of the Iomrautvaam, in the Khatyrka (river), Khatyrka ultramafic (silicon-poor) zone of the Koryak–Kamchatka fold area, Koryak Mountains, Anadyrsky District, Chukotka Autonomous Okrug, Far Eastern Federal District, Far Eastern federal districts of Russia, Federal District, Russia.Razin, L.V., N.S. Rudashevskii, and L.N. Vyal'sov. (1985) New natural intermetallic compounds of aluminum, copper and zinc – khatyrkite CuAI2, cupalite CuAI and zinc aluminides – from hyperbasites of dunite-harzburgite formation. Zap. Vses. Mineral. Obshch., 114,90–100 (in Russian). c.f. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Khatyrkite
Khatyrkite ( ) is a rare mineral which is mostly composed of copper and aluminium, but may contain up to about 15% of zinc or iron. Its chemical structure is described by an approximate formula or . It was discovered in 1985 in a placer in association with another rare mineral cupalite (). These two minerals have only been found at in the area of the Iomrautvaam, a tributary of the Khatyrka river, in the Koryak Mountains, in Anadyrsky District (former Beringovsky District), Chukotka, Russia. Analysis of one of the samples containing khatyrkite showed that the small rock was from a meteorite. A geological expedition has identified the exact place of the original discovery and found more specimens of the Khatyrka meteorite. The mineral's name derives from the Khatyrka (russian: Хатырка) zone where it was discovered. Its type specimen (defining sample) is preserved in the Mining Museum in Saint Petersburg, and parts of it can be found in other museums, such as Museo d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, opacity (optics), opacity, and lustre (mineralogy), luster, but may have properties that differ from those of the pure metals, such as increased strength or hardness. In some cases, an alloy may reduce the overall cost of the material while preserving important properties. In other cases, the mixture imparts synergistic properties to the constituent metal elements such as corrosion resistance or mechanical strength. Alloys are defined by a metallic bonding character. The alloy constituents are usually measured by mass percentage for practical applications, and in Atomic ratio, atomic fraction for basic science studies. Alloys are usually classified as substitutional or interstitial alloys, depending on the atomic arrangement that forms the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Federal Districts Of Russia
The federal districts (russian: федера́льные округа́, ''federalnyye okruga'') are groupings of the federal subjects of Russia. Federal districts are not mentioned in the nation's constitution, and do not have competences of their own and do not manage regional affairs. They exist solely to monitor consistency between the federal and regional bodies of law, and ensuring governmental control over the civil service, judiciary, and federal agencies, operating in the regions. List of federal districts ''Source'': History The federal districts of Russia were established by President Vladimir Putin in 2000 to facilitate the federal government's task of controlling the then 89 federal subjects across the country. On 19 January 2010, the new North Caucasian Federal District split from the Southern Federal District. In March 2014, after the annexation of Crimea, the Crimean Federal District was established. The legality of this annexation is disputed by an o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange. The name "corundum" is derived from the Tamil- Dravidian word ''kurundam'' (ruby-sapphire) (appearing in Sanskrit as ''kuruvinda''). Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals. It is commonly used as an abrasive on sandpaper and on large tools used in machining metals, plastics, and wood. Emery, a variety of corundum with no value a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinel
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals. Properties Spinel crystallizes in the isometric system; common crystal forms are octahedra, usually twinned. It has no true cleavage, but shows an octahedral parting and a conchoidal fracture. Its hardness is 8, its specific gravity is 3.5–4.1, and it is transparent to opaque with a vitreous to dull luster. It may be colorless, but is usually various shades of red, lavender, blue, green, brown, black, or yellow. Some spinels are among the most famous gemstones; among them are the Black Prince's Ruby and the "Timur ruby" in the British Crown Jewels, and the "Côte de Bretagne", formerly from the French Crown jewels. The Samarian Spinel is the largest known spinel in the world, weighing . The transparent red spinels were called spinel-rubies or b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vickers Hardness Test
The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The basic principle, as with all common measures of hardness, is to observe a material's ability to resist plastic deformation from a standard source. The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The hardness number can be converted into units of pascals, but should not be confused with pressure, which uses the same units. The hardness number is determined by the load over the surface area of the indentation and not t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mohs Scale Of Mineral Hardness
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by the German geologist and mineralogist Friedrich Mohs, in his book ''"Versuch einer Elementar-Methode zur naturhistorischen Bestimmung und Erkennung der Fossilien"''; it is one of several definitions of hardness in materials science, some of which are more quantitative. The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise ''On Stones'', , followed by Pliny the Elder in his ''Naturalis Historia'', . The Mohs scale is useful for identification of minerals in the field, but is not an accurate predictor of how well materials endure in an industrial setting – ''toughness''. Minerals The Mohs scale of mineral hardness is based on the ability ... [...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, 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 parallelogram or parallelepiped) that generates the whole tiling using only translations. There are two special cases of the unit cell: the primitive cell and the conventional cell. The primitive cell is a unit cell corresponding to a single lattice point, it is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formula Unit
In chemistry, a formula unit is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. Examples include ionic and and covalent networks such as and C (as diamond or graphite).Steven S. Zumdahl; Susan A. Zumdahl (2000), ''Chemistry'' (5 ed.), Houghton Mifflin, pp. 470-6, Ionic compounds do not exist as individual molecules; a formula unit thus indicates the lowest reduced ratio of ions in the compound. In mineralogy, as minerals are almost exclusively either ionic or network solids, the formula unit is used. The number of formula units (Z) and the dimensions of the crystallographic axes are used in defining the 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object 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 was complete was only ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthorhombic Crystal System
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (''a'' by ''b'') and height (''c''), such that ''a'', ''b'', and ''c'' are distinct. All three bases intersect at 90° angles, so the three lattice vectors remain mutually orthogonal. Bravais lattices There are four orthorhombic Bravais lattices: primitive orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic. For the base-centered orthorhombic lattice, the primitive cell has the shape of a right rhombic prism;See , row oC, column Primitive, where the cell parameters are given as a1 = a2, α = β = 90° it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. Note that the length a of the primiti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Museo Di Storia Naturale Di Firenze
The Museo di Storia Naturale di Firenze is a natural history museum in 6 major collections, located in Florence, Italy. It is part of the University of Florence. Museum collections are open mornings except Wednesday, and all day Saturday; an admission fee is charged. The museum was established on February 21, 1775 by Grand Duke Pietro Leopoldo as the Imperial Regio Museo di Fisica e Storia Naturale. At that time it consisted of several natural history collections housed within the palazzo Torrigiani on Via Romana. Through the past two centuries, it has grown significantly and now forms one of the finest collections in Italy. Collections Today's collections are as follows: * Giardino dei Semplici (Via Micheli, 3) - Europe's third oldest botanical garden, established in 1545, now containing some 9,000 plant specimens. * Museo di Botanica (Via La Pira, 4) - a large herbarium of approximately 4 million specimens, including the historic collections of Andrea Cesalpino (1563), claime ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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