mineral
Smoky Quartz
Silicon Dioxide (SiO2)
Hardness: 7 Mohs; Color: Brownish-grey to black; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Brownish-grey to black
- Luster
- Vitreous
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Physical properties
Hardness: 7 Mohs; Color: Brownish-grey to black; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65
Formation & geological history
Forms in intrusive igneous and metamorphic rocks, particularly pegmatites. The color is produced by natural irradiation of aluminum-bearing quartz over millions of years.
Uses & applications
Used extensively in jewelry as a gemstone, in ornamental carvings, and by crystal collectors. Historically used for making early sunglasses in China.
Geological facts
The dark color of Smoky Quartz is caused when silicon dioxide is exposed to natural radiation from surrounding radioactive elements like uranium or thorium in the host rock.
Field identification & locations
Identify by its translucent brownish color and glassy luster. It can be found globally, with major deposits in Brazil, Madagascar, and the Swiss Alps.
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