mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-gray to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

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

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brownish-gray to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65

Formation & geological history

Forms in igneous and metamorphic rocks, particularly pegmatites. The color is caused by natural irradiation of aluminum-bearing quartz over millions of years.

Uses & applications

Used in jewelry, decorative carvings, lapidary arts, and as a healing crystal in metaphysical practices. Also used in historical sunglasses in China.

Geological facts

The dark color is stable up to about 200 degrees Celsius, after which it may turn yellow or colorless. Cairngorm is a famous variety found in the Cairngorm Mountains of Scotland.

Field identification & locations

Identify by its glassy look, lack of cleavage, 6-sided crystal habits (if present), and the ability to scratch glass. Commonly found in quartz veins and granite cavities globally.