mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Hardness: 7 on the Mohs scale; Color: Grayish-brown to black transition; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Grayish-brown to black transition
Luster: Vitreous (glassy)

Identified March 25, 2026More mineral →

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Physical properties

Hardness: 7 on the Mohs scale; Color: Grayish-brown to black transition; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed in igneous or metamorphic rocks (especially pegmatites). The smoky color is caused by natural gamma irradiation from surrounding minerals acting on trace aluminum impurities within the crystal lattice.

Uses & applications

Used in gemstone jewelry, ornamental carvings, and specialized electronics (though synthetic quartz is more common for tech). It is highly popular among crystal collectors/enthusiasts.

Geological facts

Smoky Quartz is the national gemstone of Scotland, where it is known as 'Cairngorm.' It was used in China as early as the 12th century to make the first primitive sunglasses.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its glassy luster, and the lack of cleavage. Often found near granite outcrops. Common locations include Brazil, the Swiss Alps, and Colorado (USA).