mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Grey, brownish-grey to black; Luster: Vitreous; Crystal system: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grey, brownish-grey to black
Luster: Vitreous

Identified April 12, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, brownish-grey to black; Luster: Vitreous; Crystal system: Trigonal/Hexagonal; 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 decorative gemstones, in jewelry (faceting or cabochons), and as metaphysical/collectible specimens. Occasionally used in optics and electronics.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as Cairngorm. Historically, the first sunglasses were made from flat panes of smoky quartz in 12th-century China.

Field identification & locations

Identify in the field by its distinct grey-translucent color, lack of cleavage, and ability to scratch glass easily. Commonly found in mountainous regions such as the Swiss Alps, Brazil, and the United States (Colorado).