mineral
Smoky Quartz and Citrine
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Smoky grey-brown and pale yellowish-gold, Luster: Vitreous (glassy), Crystal system: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Smoky grey-brown and pale yellowish-gold, Luster: Vitreous (glassy), Crystal system: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed in igneous and metamorphic environments, specifically pegmatites and hydrothermal veins. These specimens are tumbled, meaning they were smoothed in a rotary machine to mimic river-worn erosion.
Uses & applications
Used primarily in jewelry, as ornamental stones, for crystal collecting, and historical use in early optical components.
Geological facts
Naturally occurring Citrine is rare; much commercial citrine is actually heat-treated Amethyst. Smoky quartz gets its color from natural irradiation of aluminum impurities within the crystal lattice.
Field identification & locations
Identify by their glassy luster and hardness (cannot be scratched by a steel knife). Common locations include Brazil, Madagascar, and the United States (Colorado).
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