mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Mohs hardness of 7, vitreous luster, hexagonal crystal system (trigonal). Usually translucent to opaque with a smoky brown to grey color. White streak and conchoidal fracture.

Identified July 13, 2026More mineral →

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Physical properties

Mohs hardness of 7, vitreous luster, hexagonal crystal system (trigonal). Usually translucent to opaque with a smoky brown to grey color. White streak and conchoidal fracture.

Formation & geological history

Forms in intrusive igneous rocks (pegmatites) and metamorphic rocks. The smoky color is caused by natural gamma irradiation of the trace aluminum within the crystal lattice over millions of years.

Uses & applications

Used extensively in jewelry, ornamental carvings, and by collectors. In industry, quartz is used in glassmaking and electronics (piezoelectric properties), though smoky varieties are usually reserved for aesthetics.

Geological facts

Smoky Quartz was one of the first materials used for sunglasses in 12th century China to hide the expressions of judges in court. It is the national gem of Scotland, where it is known as Cairngorm.

Field identification & locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent 'smoky' appearance. Commonly found in Brazil, Madagascar, and the Swiss Alps.