mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

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

Identified March 28, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-black; Luster: Vitreous; Crystal structure: Hexagonal (Trigonal); 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 produced by natural irradiation of trace aluminum impurities within the crystal structure over millions of years.

Uses & applications

Used in gemstone jewelry (faceting and cabochons), crystal healing collections, and historically in the creation of the first sunglasses in 12th century China.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often called 'Cairngorm' after the mountain range where it is traditionally mined. The color can be deepened through artificial gamma irradiation.

Field identification & locations

Identify in the field by its hardness (scratches glass), glass-like luster, and lack of cleavage. It is commonly found in Brazil, Madagascar, the Swiss Alps, and the United States (Colorado, New Hampshire). Collectors should look for clarity and internal 'veils' or inclusions.