mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

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

Identified July 15, 2026More mineral →

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Physical properties

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

Formation & geological history

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

Uses & applications

Used primarily as a gemstone in jewelry, decorative ornaments, and as a popular specimen for mineral collectors. Some industrial use in electronics, though synthetic quartz is more common.

Geological facts

Smoky quartz gets its dark color from exposure to natural radiation from surrounding radioactive elements like uranium or thorium. Crystals can range from almost transparent to completely opaque black.

Field identification & locations

Identify by its characteristic 'smoky' translucency and 7 Mohs hardness (scratches glass). Commonly found in the Swiss Alps, Brazil, and Pikes Peak, Colorado. To field identify, look for hexagonal crystal faces and smoky coloration that does not rub off.