mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey, smoky yellow, to nearly black; Luster: Vitreous (glassy); Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brownish-grey, smoky yellow, to nearly black
Luster: Vitreous (glassy)

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic rocks like pegmatites and granites. The smoky color results from free silicon formed from silicon dioxide by natural irradiation of the crystal.

Uses & applications

Used in gemstone jewelry, ornamental carvings, clock oscillators, and for metaphysical collecting.

Geological facts

It is the national gem of Scotland, where it is known as 'Cairngorm.' The dark color is often stable but can fade if exposed to intense sunlight for long periods.

Field identification & locations

Identify by its translucent brownish 'smoke' color and glass-like luster. Commonly found in Brazil, Madagascar, and the USA (Colorado). Collectors look for clarity and depth of color.