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Chert (/ tʃ ɜːr t /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.
Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically [1] in thin section by transmitted polarized light. Among the sedimentary rocks , chert and flint are cryptocrystalline.
Chalcedony (/ k æ l ˈ s ɛ d ə n i / kal-SED-ə-nee or / ˈ k æ l s ə ˌ d oʊ n i / 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.
Cryptocrystalline quartz A piece of flint 9–10 cm (3.5–3.9 in) long, weighing 171 grams Flint , occasionally flintstone , is a sedimentary cryptocrystalline form of the mineral quartz , [ 1 ] [ 2 ] categorized as the variety of chert that occurs in chalk or marly limestone .
Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. [10] Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation ...
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal.
Ametrine, also known as trystine, golden amethyst, or by the trade name bolivianite, is a variety of quartz with alternating zones of purple and yellow-orange coloration. Its name is a portmanteau of amethyst and citrine. While ametrine is commonly referred to as a combination of these two quartz varieties, some sources claim this is not ...
This property is used to grow single crystals of quartz in a hydrothermal process where natural quartz is dissolved in superheated water in a pressure vessel that is cooler at the top. Crystals of 0.5–1 kg can be grown for 1–2 months. [12] These crystals are a source of very pure quartz for use in electronic applications. [15]