mineral

Smoky Quartz

Silicon Dioxide (SiO2) with trace aluminum and irradiation

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 14, 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 pegmatites and hydrothermal veins. The color is caused by natural irradiation of trace aluminum impurities within the quartz crystal over millions of years.

Uses & applications

Used primarily in jewelry (beads, cabochons), as an ornamental stone in home decor, and historically in the first primitive sunglasses made in China in the 12th century.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountains where it is found. Very dark, opaque varieties are commonly called 'Morion'.

Field identification & locations

Identify in the field by its hardness (will scratch glass but not topaz), its conchoidal (glass-like) fracture pattern, and its distinctive smoky translucency. Common in granite-rich regions like Brazil, USA, and the Swiss Alps.

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