mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 Mohs; Color: Brownish-grey to black; Luster: Vitreous (glassy); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 Mohs
Color: Brownish-grey to black
Luster: Vitreous (glassy)

Identified July 21, 2026More mineral →

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Physical properties

Hardness: 7 Mohs; Color: Brownish-grey to black; Luster: Vitreous (glassy); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in igneous or metamorphic rocks (especially granite pegmatites) through hydrothermal activity. The color results from natural irradiation of aluminum-bearing quartz over millions of years.

Uses & applications

Used extensively in jewelry (faceting and cabochons), as an ornamental stone, in spiritual practices, and as collector specimens.

Geological facts

The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. Specimens that are nearly opaque and black are known as 'Morion'.

Field identification & locations

Identify by its characteristic glassy transparency combined with its smoky color and lack of cleavage (it breaks like glass). Common in mountainous regions like the Alps, Colorado, and Brazil.