mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

Hardness: 7 on Mohs scale
Color: Grayish-brown to black
Luster: Vitreous

Identified June 16, 2026More mineral →

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Physical properties

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

Formation & geological history

Forms in igneous and metamorphic rocks, specifically in pegmatites and hydrothermal veins. The smoky color is caused by natural radiation from surrounding rocks acting on aluminum impurities within the quartz crystal.

Uses & applications

Used in jewelry as a gemstone, in crystal healing practices, and as decorative carvings or specimens for collectors. In industry, quartz is used for its piezoelectric properties and in glass making.

Geological facts

The dark color of smoky quartz can often be reversed by heating the specimen. It is the national gem of Scotland, where it is known as Cairngorm.

Field identification & locations

Identify in the field by its hardness (will scratch glass), conchoidal fracture, and characteristic smoky translucency. Found globally, with major deposits in Brazil, Madagascar, and the Swiss Alps.