mineral

Smoky Quartz

Silicon Dioxide (SiO2) with aluminum impurities

Hardness: 7 on Mohs scale; Color: Grey, brown, to nearly black; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grey, brown, to nearly black
Luster: Vitreous

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grey, brown, to nearly black; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Formation & geological history

Formed in igneous or metamorphic environments, particularly pegmatites and hydrothermal veins. Its characteristic color is caused by natural radiation (from surrounding rock) acting on trace amounts of aluminum within the crystal lattice.

Uses & applications

Used in jewelry (faceted or cabochon), ornamental carvings, crystal healing practices, and as a popular collector's specimen.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountains where it was historically found. 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 hexagonal crystal habit, smoky translucence, and lack of cleavage (conchoidal fracture). Commonly found in Brazil, Madagascar, Switzerland, and US states such as Colorado and North Carolina.

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