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  2. Jasper - Wikipedia

    en.wikipedia.org/wiki/Jasper

    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 ...

  3. Chalcedony - Wikipedia

    en.wikipedia.org/wiki/Chalcedony

    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.

  4. Herkimer diamond - Wikipedia

    en.wikipedia.org/wiki/Herkimer_diamond

    Herkimer diamonds are double-terminated quartz crystals discovered within exposed outcrops of dolomite in and around Herkimer County, New York, and the Mohawk River Valley in the US. [1][2] They are not diamonds; the "diamond" in their name is due to both their clarity and well formed faces. Because the first discovery sites were in the village ...

  5. Smoky quartz - Wikipedia

    en.wikipedia.org/wiki/Smoky_quartz

    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 ...

  6. Chert - Wikipedia

    en.wikipedia.org/wiki/Chert

    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.

  7. Moss agate - Wikipedia

    en.wikipedia.org/wiki/Moss_agate

    Moss agate. Moss agate is a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green color embedded in the stone, forming filaments and other patterns suggestive of moss. [1] The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron.

  8. Flint - Wikipedia

    en.wikipedia.org/wiki/Flint

    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 ...

  9. Quartz - Wikipedia

    en.wikipedia.org/wiki/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 and ...

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