mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Brownish gray to black; Luster: Vitreous; Crystal Structure: Trigonal (hexagonal prisms); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brownish gray to black
Luster: Vitreous

Identified May 20, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Brownish gray to black; Luster: Vitreous; Crystal Structure: Trigonal (hexagonal prisms); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

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

Uses & applications

Used primarily in jewelry as a gemstone, decorative carvings, and as a popular specimen for mineral collectors. Some industrial use in electronics, though synthetic quartz is more common there.

Geological facts

The dark color is the result of free silicon formed from silicon dioxide by natural irradiation. It was historically used in China to make the first 'sunglasses' in the 12th century.

Field identification & locations

Identify by its hexagonal crystal shape, lack of cleavage, and translucent smoky-brown color. Found globally, with notable deposits in Brazil, Madagascar, and the Swiss Alps.