gemstone
Smoky Quartz
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Gray to brownish-black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Gray to brownish-black
- Luster
- Vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Gray to brownish-black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed in igneous or metamorphic rocks (especially pegmatites) via natural irradiation of aluminum-bearing quartz over millions of years.
Uses & applications
Used primarily in jewelry, ornamental carvings, and as healing crystals or collector specimens.
Geological facts
The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. It is the national gem of Scotland, where it is often called Cairngorm.
Field identification & locations
Identify by its translucent smoky color and glass-like luster. Found globally, with notable deposits in Brazil, Switzerland, and the United States (Colorado).
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