mineral
Smoky Quartz (with Iron Inclusions)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-brown to smoky black with orange iron staining; Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-brown to smoky black with orange iron staining
- Luster
- Vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-brown to smoky black with orange iron staining; Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in igneous and metamorphic rocks, specifically pegmatites and hydrothermal veins, through the natural irradiation of aluminum-bearing quartz over millions of years.
Uses & applications
Used in jewelry, decorative ornaments, gemstone collecting, and historically in early sunglasses and optical instruments.
Geological facts
The 'smoky' color is caused by natural radiation from surrounding rocks that activates aluminum impurities within the crystal lattice. It is the national gem of Scotland, where it is known as Cairngorm.
Field identification & locations
Look for a translucent to transparent glass-like texture with a smoky tint and a lack of cleavage. Often found near granite outcrops. To identify: it should easily scratch glass but not be scratched by a steel knife.
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