mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Translucent to opaque, varying from light grey to dark brownish-black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Luster: Vitreous (glassy)

Identified January 1, 2026More mineral →

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Physical properties

Formation & geological history

Forms in igneous and metamorphic rocks, particularly granites and pegmatites. The smoky color is caused by natural irradiation from surrounding radioactive minerals which facilitates the displacement of electrons within the crystal lattice of the quartz.

Uses & applications

Used in the gemstone and jewelry industry as beads, facets, or cabochons. It is also a popular collector's mineral and is sometimes used in the manufacturing of optical instruments and electronics due to its piezoelectric properties.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the Cairngorm Mountains. Very dark, opaque varieties are sometimes referred to as 'Morion'. Most of the world's supply is sourced from Brazil, Madagascar, and the USA.

Field identification & locations

Identify in the field by its distinct brownish-to-black transparency and its ability to scratch glass (hardness 7). Look for it in quartz veins or granitic pockets. It will lack the perfect cleavage planes found in similar-looking minerals like dark calcite or fluorite.