mineral
Smoky Quartz
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Brownish-grey to black; Luster: Vitreous; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brownish-grey to black
- Luster
- Vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-grey to black; Luster: Vitreous; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Forms in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The color is caused by natural irradiation of aluminum-bearing quartz.
Uses & applications
Used in jewelry, decorative carvings, and as a popular specimen for collectors. In industry, quartz is used for its piezoelectric properties and in glass making.
Geological facts
The dark color is the result of free silicon formed from silicon dioxide by natural irradiation. Cairngorm is a type of smoky quartz found in the Cairngorm Mountains of Scotland.
Field identification & locations
Identify by its characteristic smoky translucence and hardness (it will scratch glass). Commonly found in granite-rich mountainous regions worldwide such as the Swiss Alps and Brazil.
