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Microcrystalline or cryptocrystalline quartz. Chert (/ tʃɜːrt /) 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 ...
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.
Quartz. 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 ...
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. Historically, flint was widely used to make stone tools and start fires. Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones ...
Cryptocrystalline. 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. Carbonado, a form of diamond, is also cryptocrystalline.
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, [1][2] is an opaque, [3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron (III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as ...
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 translucent to opaque green ...
Chrysoprase - Szklary, Lower Silesia, Poland. Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its color is normally apple-green, but varies from turquoise -like cyan to deep green. The darker varieties of chrysoprase are also referred to ...