mineral

Smoky Quartz

Quartz (Silicon Dioxide), Formula: SiO2

Hardness: 7 on the Mohs scale; Color: Brownish gray to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Hardness: 7 on the Mohs scale
Color: Brownish gray to black
Luster: Vitreous (glassy)

Identified March 18, 2026More mineral →

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Physical properties

Hardness: 7 on the Mohs scale; Color: Brownish gray to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks like granite and gneiss. The smoky color is produced by natural irradiation of aluminum-bearing quartz from surrounding radioactive minerals in the earth's crust.

Uses & applications

Used primarily in lapidary work for jewelry, ornamental carvings, and home decor. Also popular among mineral collectors and used in crystal healing practices.

Geological facts

The dark color is due to the bombardment of the crystal by radioactive rays from surrounding minerals, which displaces electrons from trace aluminum impurities. It is the national gem of Scotland, where it is known as 'Cairngorm.'

Field identification & locations

Identify by its translucent brownish-gray hue, glassy luster, and the fact that it can scratch glass but cannot be scratched by a steel knife. Common locations include Brazil, Madagascar, Switzerland, and the United States (Colorado).

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