mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Brown to blackish-drab to smoky gray, Luster: Vitreous, Crystal structure: Hexagonal (trigonal), Cleavage: None, Specific gravity: 2.65

Identified April 29, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brown to blackish-drab to smoky gray, Luster: Vitreous, Crystal structure: Hexagonal (trigonal), Cleavage: None, Specific gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, particularly granite pegmatites and hydrothermal veins. The smoky color is caused by natural gamma irradiation of the aluminum-bearing mineral over millions of years.

Uses & applications

Used extensively in jewelry, ornamental carvings, and by collectors. In industry, it was historically used for early eyeglasses in China and is still used in gemstone therapy and metaphysical practices.

Geological facts

The dark color is a result of structural defects in the crystal lattice where aluminum replaces silicon. When heated, smoky quartz can turn yellow and be sold as fake 'citrine'. Darkest varieties are known as 'Morion'.

Field identification & locations

Identified by its distinctive smoky translucency and hexagonal crystal shape. Commonly found in Brazil, the Swiss Alps, Madagascar, and the United States (Colorado). Field identification involves checking hardness against steel and observing the conchoidal fracture.