mineral

Smoky Quartz (Tumbled)

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 20, 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 or metamorphic rocks (especially granitic pegmatites) through hydrothermal activity. The smoky color results from natural irradiation of aluminum impurities in the crystal lattice over millions of years.

Uses & applications

Used primarily in lapidary work, jewelry, and as a popular semi-precious stone for gemstone collectors and metaphysical uses. Historically used for making early sunglasses in 12th century China.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the Cairngorm Mountains where it was traditionally mined.

Field identification & locations

Identify by its 'smoky' translucency and hardness (will scratch glass). Commonly found in Brazil, Madagascar, and the USA. Collectors look for clarity and absence of heavy inclusions when choosing tumbled specimens.