mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale. Color: Brown to black, smoky gray. Luster: Vitreous (glassy). Crystal structure: Trigonal/Hexagonal. Cleavage: Indistinct/Conchoidal fracture. Specific gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Brown to black, smoky gray
Luster: Vitreous (glassy)

Identified April 20, 2026More mineral →

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Physical properties

Hardness: 7 on the Mohs scale. Color: Brown to black, smoky gray. Luster: Vitreous (glassy). Crystal structure: Trigonal/Hexagonal. Cleavage: Indistinct/Conchoidal fracture. Specific gravity: 2.65.

Formation & geological history

Forms in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The color is caused by natural irradiation of aluminum impurities within the crystal lattice over millions of years.

Uses & applications

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

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. In ancient China, it was used to make the first sunglasses to help judges hide their facial expressions.

Field identification & locations

Identify by its smoky translucence, lack of cleavage, and ability to scratch glass. Found globally, with notable deposits in the Swiss Alps, Brazil, Madagascar, and the United States (Colorado and New Hampshire).