mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Smoky brown to brownish-gray, Luster: Vitreous (glassy), Crystal Structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified May 14, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Smoky brown to brownish-gray, Luster: Vitreous (glassy), Crystal Structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Forms in igneous rocks (granite pegmatites) and metamorphic rocks through hydrothermal processes. The smoky color is caused by natural irradiation from surrounding rocks affecting traces of aluminum within the crystal lattice.

Uses & applications

Used primarily in lapidary work, jewelry, and as a popular specimen for mineral collectors. Some industrial use in glass and oscillators, though synthetic quartz is now more common.

Geological facts

Cairngorm is a famous variety of smoky quartz found in the Cairngorm Mountains of Scotland. In the 12th century, flat panes of smoky quartz were used in China as the world's first sunglasses.

Field identification & locations

Identified by its tea-colored transparency, hardness that scratches glass, and lack of cleavage. Often found in mountain ranges, alluvial gravels, and riverbeds near granite outcrops.