mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7.0 on Mohs scale; Color: translucent brownish-grey to black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7
Color: translucent brownish-grey to black
Luster: Vitreous

Identified March 21, 2026More mineral →

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Physical properties

Hardness: 7.0 on Mohs scale; Color: translucent brownish-grey to black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in igneous or metamorphic rocks (especially pegmatites) through natural irradiation of aluminum-bearing quartz. Most specimens range from millions to hundreds of millions of years old.

Uses & applications

Primary uses include jewelry (as a gemstone), ornamental carvings, and spiritual/metaphysical collecting. Also used in historical industrial applications for optical precision.

Geological facts

The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. Cairngorm is a famous variety found in the Cairngorm Mountains of Scotland. It is the national gem of Scotland.

Field identification & locations

Identify in the field by its distinct smoky transparency, lack of cleavage, and ability to scratch glass. Commonly found in Brazil, Madagascar, USA (Colorado/New Hampshire), and the Swiss Alps.