mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Grayish-brown to black, translucent to opaque; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Grayish-brown to black, translucent to opaque
Luster: Vitreous (glassy)

Identified March 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The brown color results from natural irradiation of aluminum-bearing quartz over millions of years of geological time.

Uses & applications

Used in the gemstone and jewelry industry, as decorative ornamental pieces, in metaphysical healing practices, and as collector specimens.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountains where it is found. Its dark color is caused by the same type of radiation that turns quartz purple into amethyst, but involves different trace elements.

Field identification & locations

Identify in the field by its hardness (scratches glass), glass-like luster, and lack of cleavage. Commonly found in granite outcroppings, riverbeds, and mountainous regions worldwide including Brazil, Madagascar, and the Swiss Alps.