mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Brownish-grey, translucent to nearly opaque; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brownish-grey, translucent to nearly opaque
Luster: Vitreous (glassy)

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic rocks like granite or gneiss. The smoky color is produced by natural irradiation of aluminum-bearing quartz over millions of years of geological time.

Uses & applications

Used in jewelry (faceted or cabochons), as decorative ornamental stones, and in the production of glass and electronic precision instruments.

Geological facts

Smoky quartz is the national gemstone of Scotland, where it is often referred to as 'Cairngorm' after the mountain range where it is traditionally found. It was used for sunglasses in 12th century China.

Field identification & locations

Identify in the field by its hardness (will scratch glass), glassy luster, and lack of cleavage planes. Commonly found in pegmatite veins and alpine clefts. Collectors should look for crystal faces or transparency.