Tag: Quartz
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Hexagonal – Hexagonal prism (six-sided)
Common examples include: emerald, galena, quartz, hanksite, vanadinite
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Sceptered – Crystal growth stops and continues at the top of the crystal, but not at the bottom
Common examples include: hedenbergite, quartz
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Hopper – Like cubic, but outer portions of cubes grow faster than inner portions creating a concavity
Common examples include: halite, calcite, synthetic bismuth A hopper crystal is a form of crystal, the shape of which resembles that of a pyramidal hopper container. The edges of hopper crystals are fully developed, but the interior spaces are not filled in. This results in what appears to be a hollowed out step lattice formation, as if someone had removed interior sections of the…
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Granular – Aggregates of diminute anhedral crystals in matrix or other surface
Common examples include: andradite, bornite, scheelite, quartz
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Druse, encrustation – Aggregate of crystals coating a surface or cavity, usually found in geodes
Common examples: azurite, celestine, calcite, uvarovite, malachite, quartz In geology, druse refers to a coating of fine crystals on a rock fracture surface or vein or within a vug or geode. See also References
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Concentric – Circular ring aggregates around a center
This habit is found in cross-sections from reniform/mamillary habits, and also from elongated stalactites of amethyst (quartz), malachites, rhodocrosite, and others Common examples include: quartz, malachite, rhodocrosite
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Chert
Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. Chert is typically composed of the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon…
