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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 ...
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Spinel Group
The spinels are any of a class of minerals of general formulation which crystallise in the cubic (isometric) crystal system, with the X anions (typically chalcogens, like oxygen and sulfur) arranged in a cubic close-packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice.H-J MeyerFestkörperchemiein: H-J Meyer (ed.), ''Riedel Moderne Anorganische Chemie'', Walter de Gruyter, 2012, . Retrieved 15 April 2018. Although the charges of A and B in the prototypical spinel structure are +2 and +3, respectively (), other combinations incorporating divalent, trivalent, or tetravalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon, are also possible. The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel. A and B can also be the same metal with different valences, as is the case with magnetite, (as ), whic ...
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Spinel Group
The spinels are any of a class of minerals of general formulation which crystallise in the cubic (isometric) crystal system, with the X anions (typically chalcogens, like oxygen and sulfur) arranged in a cubic close-packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice.H-J MeyerFestkörperchemiein: H-J Meyer (ed.), ''Riedel Moderne Anorganische Chemie'', Walter de Gruyter, 2012, . Retrieved 15 April 2018. Although the charges of A and B in the prototypical spinel structure are +2 and +3, respectively (), other combinations incorporating divalent, trivalent, or tetravalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon, are also possible. The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel. A and B can also be the same metal with different valences, as is the case with magnetite, (as ), whic ...
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Black Prince's Ruby
The Black Prince's Ruby is a large, irregular cabochon red spinel weighing set in the cross pattée above the Cullinan II diamond at the front of the Imperial State Crown of the United Kingdom. The spinel is one of the oldest parts of the Crown Jewels of the United Kingdom, with a history dating back to the middle of the 14th century. It has been in the possession of England's rulers since it was given in 1367 to its namesake, Edward of Woodstock (the "Black Prince"). The stone is believed to have originated from the Badakhshan mines in present day Afghanistan and Tajikistan, the principal source of large spinel gems in the Middle Ages. Spinel All red gemstones used to be referred to as rubies or "balas rubies". It was not until 1783 that spinels were chemically differentiated from rubies. They both have aluminium, oxygen, and a little chromium, but spinels also have magnesium, which rubies lack. History Don Pedro of Seville The Black Prince's Ruby dates back to the mi ...
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Crown Jewels Of The United Kingdom
The Crown Jewels of the United Kingdom, originally the Crown Jewels of England, are a collection of royal ceremonial objects kept in the Tower of London which include the coronation regalia and vestments worn by British monarchs. Symbols of over 800 years of monarchy, the coronation regalia are the only working set in Europe and the collection is the most historically complete of any regalia in the world. Objects used to invest and crown British monarchs variously denote their role as head of state of the United Kingdom and other countries of the Commonwealth, Supreme Governor of the Church of England, and head of the British armed forces. They feature heraldic devices and national emblems of England, Scotland, Wales and Northern Ireland. Use of regalia by monarchs in England can be traced back to when it was converted to Christianity in the Early Middle Ages. A permanent set of coronation regalia, once belonging to Edward the Confessor, was established after he was made a s ...
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Crystal Twinning
Crystal twinning occurs when two or more adjacent crystals of the same mineral are oriented so that they share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals that are tightly bonded to each other. The surface along which the lattice points are shared in twinned crystals is called a composition surface or twin plane. Crystallographers classify twinned crystals by a number of twin laws. These twin laws are specific to the crystal structure. The type of twinning can be a diagnostic tool in mineral identification. Deformation twinning, in which twinning develops in a crystal in response to a shear stress, is an important mechanism for permanent shape changes in a crystal.Courtney, Thomas H. (2000) ''Mechanical Behavior of Materials'', 2nd ed. McGraw Hill. Definition Twinning is a form of symmetrical intergrowth between two or more adjacent crystals of the same mineral. It differs from the ordinary random i ...
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Timur Ruby
The Timur Ruby (also ''Khiraj-i-alam'', "Tribute to the World") is an unfaceted, polished red spinel set in a necklace. It is named after the ruler Timur,Morgan, Diane (2008). ''Fire and Blood: Rubies in Myth, Magic, and History.'' Greenwood Publishing Group, founder of the Timurid Empire and purportedly one of its former owners. It was believed to be a ruby until 1851. It is inscribed with the titles of five of its previous owners: Jahangir (who also had the name of his father Akbar the Great inscribed), Shah Jahan, Farrukhsiyar, Nader Shah and Ahmad Shah Durrani.Ball V. (1894)A Description of Two Large Spinel Rubies, with Persian Characters Engraved upon Them.''Proceedings of the Royal Irish Academy'' Vol. 3, (1893 - 1896), pp. 380-400 Since 1612, the owners of the Timur ruby have also owned the Koh-i-Noor diamond. It has been in the possessions of the Safavid, Mughal, Sikh and British empires, and is currently part of the British crown jewels . History Origins Spinels ...
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Oxide Minerals
The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. The minerals with complex anion groups such as the silicates, sulfates, carbonates and phosphates are classed separately. Simple oxides: *XO **Periclase group *** Periclase *** Manganosite **Zincite group *** Zincite *** Bromellite ***Tenorite ***Litharge * **Cuprite ** Ice * **Hematite group ***Corundum ***Hematite ***Ilmenite * **Rutile group ***Rutile ***Pyrolusite ***Cassiterite **Baddeleyite **Uraninite **Thorianite * **Spinel group ***Spinel ***Gahnite ***Magnetite ***Franklinite ***Chromite ** Chrysoberyl **Columbite *Hydroxide subgroup: **Brucite ** Manganite **Romanèchite **Goethite group: ***Diaspore *** Goethite Nickel–Strunz Classification -04- Oxides IMA-CNMNC proposes a new hierarchical scheme (Mills et al., 2009). This list uses it ...
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Aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has a great affinity towards oxygen, and forms a protective layer of oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, non-magnetic and ductile. It has one stable isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of 26Al is used in radiodating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it is polarizing, and bonds aluminium forms tend towards covalency. The strong affinity tow ...
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Badakhshan
Badakhshan is a historical region comprising parts of modern-day north-eastern Afghanistan, eastern Tajikistan, and Taxkorgan Tajik Autonomous County in China. Badakhshan Province is one of the 34 provinces of Afghanistan. Much of historic Badakhshan lies within Tajikistan's Gorno-Badakhshan Autonomous Region, in the southeastern part of the country. The music of Badakhshan is an important part of the region's cultural heritage. Name The name "Badakhshan" ( fa, بدخشان, ''Badaxšân''; ps, بدخشان; tg, Бадахшон, ''Badaxşon''; ) is derived from the Sasanian official title ''bēdaxš'' or ''badaxš'', which may be from an earlier *pati-axša; the suffix -''ān'' indicates that the country belonged, or had been assigned as a fief, to a person holding the rank of a '' badaxš''. People Badakhshan has a diverse ethnolinguistic and religious community. Tajiks and Pamiris are the majority while a tiny minority of Kyrgyzs and Uzbeks also are found in thei ...
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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 ...
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Metamorphic Rock
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causing profound physical or chemical changes. During this process, the rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be an igneous, sedimentary, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by their protolith, their chemical and mineral makeup, and their texture. They may be formed simply by being deeply buried beneath the Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from tectonic processes such as continental collisions, which cause horizontal pressure, friction, and dis ...
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