mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Brownish-grey, black, or smoky, Luster: Vitreous (glassy), Crystal System: Hexagonal/Trigonal, Specific Gravity: 2.65.

Identified April 18, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish-grey, black, or smoky, Luster: Vitreous (glassy), Crystal System: Hexagonal/Trigonal, Specific Gravity: 2.65.

Formation & geological history

Formed in igneous and metamorphic rocks, particularly granite and pegmatites. The smoky color is created when natural radiation from surrounding rocks hits the crystal structure of clear quartz containing aluminum impurities.

Uses & applications

Used in gemstone manufacturing, jewelry (rings, pendants), decorative carving, and as a collector's mineral specimen. Historically used in the first sunglasses in 12th century China.

Geological facts

Smoky quartz is the national gemstone of Scotland, where it is often referred to as 'Cairngorm'. It can vary from translucent to nearly opaque.

Field identification & locations

Identify by its hardness (scratches glass), glass-like luster, and characteristic 'conchoidal' (shell-like) fracture. Commonly found in Brazil, Switzerland, and the United States (Colorado).