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Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO 4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO 2. Quartz is, therefore, classified structurally as a framework silicate mineral and ...
Aphanites (adj. aphanitic; from Ancient Greek αφανης (aphanḗs) 'invisible') are igneous rocks that are so fine-grained that their component mineral crystals are not visible to the naked eye [2] (in contrast to phanerites, in which the crystals are visible to the unaided eye). This geological texture results from rapid cooling in ...
Transparency and translucency. Dichroic filters are created using optically transparent materials. In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions are ...
Smoky quartz. Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystals. [6] The color of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within ...
Durr Al Najaf (Arabic: دُر ٱلنَّجَف) is a glossy and clear gemstone from the quartz family. The name means "pearl of Najaf" as it can only be sourced from Wadi-al-Salaam (Arabic: وادي السلام, romanized: Wādī al-Salām, lit. 'Valley of Peace') in Najaf, Iraq. The gemstone is found along the west of Najaf close by the Najaf ...
Chalcedony. Chalcedony (/ kælˈsɛdəni / kal-SED-ə-nee, or / ˈkælsəˌdoʊni / KAL-sə-doh-nee) [2] is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. [3] These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic.
In the hexagonal family, the crystal is conventionally described by a right rhombic prism unit cell with two equal axes (a by a), an included angle of 120° (γ) and a height (c, which can be different from a) perpendicular to the two base axes. The hexagonal unit cell for the rhombohedral Bravais lattice is the R-centered cell, consisting of ...
Heliotrope (mineral) The mineral aggregate heliotrope (from Ancient Greek ἥλιος (hḗlios) 'sun' and τρέπειν (trépein) 'to turn'), also called Indian bloodstone or ematille, is a cryptocrystalline mixture of quartz that occurs mostly as jasper (opaque) or sometimes as chalcedony (translucent). The "classic" bloodstone is ...
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