mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey, translucent; Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brownish-grey, translucent
Luster: Vitreous (glassy)

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brownish-grey, translucent; Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, specifically pegmatites and hydrothermal veins. The color is caused by natural irradiation acting on traces of aluminum within the crystal lattice.

Uses & applications

Used in the gemstone and jewelry industry, as decorative ornamental stones, and in metaphysical collecting. Historically used for making crystal spheres and early sunglasses in 12th century China.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. Some of the darkest varieties are called 'Morion'. Its dark color can be reversed through heating to approximately 200°C.

Field identification & locations

Identify in the field by its distinct conchoidal fracture, 7 hardness (scratches glass but not vice versa), and lack of cleavage. Commonly found in mountainous regions like the Alps, Brazil, and the United States (Colorado).