mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: brownish-grey, black, or smoky; Luster: vitreous (glassy); Crystal Structure: hexagonal (trigonal); Cleavage: none; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: brownish-grey, black, or smoky
Luster: vitreous (glassy)

Identified April 6, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: brownish-grey, black, or smoky; Luster: vitreous (glassy); Crystal Structure: hexagonal (trigonal); Cleavage: none; Specific Gravity: 2.65

Formation & geological history

Forms in igneous and metamorphic rocks, particularly granite and pegmatites. The smoky color is caused by natural radiation from surrounding minerals acting on trace amounts of aluminum within the crystal lattice.

Uses & applications

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

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the Cairngorm Mountains. It has been used for hundreds of years in traditional Scottish jewelry and Highland dress.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife), its glassy luster, and the characteristic conchoidal (shell-like) fracture. Found worldwide, with major deposits in Brazil, Switzerland, and the USA.