mineral

Smoky Quartz

Silicon Dioxide (SiO2) with aluminum impurities

Hardness: 7 on Mohs scale; Color: tea-colored, black, or brown; Luster: Vitreous; Crystal system: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: tea-colored, black, or brown
Luster: Vitreous

Identified April 6, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: tea-colored, black, or brown; Luster: Vitreous; Crystal system: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65.

Formation & geological history

Forms in igneous rocks like pegmatites and granites, or in metamorphic rocks. The brown color is created when crystal quartz is exposed to natural gamma radiation from surrounding minerals, which activates aluminum impurities.

Uses & applications

Used in gemstone jewelry, ornamental carvings, and by collectors. Historically used in early sunglasses in China and for piezoelectric components in electronics.

Geological facts

Smoky quartz is the national gemstone of Scotland, where it is often referred to as 'Cairngorm' after the mountain range where it was historically found.

Field identification & locations

Identify by its characteristic transparency, smoky brown to gray color, and hexagonal crystal habit. It won't be scratched by a steel knife. Common locations include Brazil, USA (Colorado), Switzerland, and Madagascar.

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