mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Hardness: 7.0 on the Mohs scale. Color: Brown to blackish, semi-transparent. Luster: Vitreous (glassy). Crystal Structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7
Color: Brown to blackish, semi-transparent
Luster: Vitreous (glassy)

Identified March 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermally filled veins. The smoky color is the result of natural irradiation of trace aluminum impurities within the crystal structure over millions of years.

Uses & applications

Commonly used in jewelry (faceting and cabochons), ornamental carvings, and 'metaphysical' collecting. Industrially used in making oscillators for watches and equipment, though synthetic quartz is more common now.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm.' Large crystals can grow to over 100 pounds. Its dark color can be removed by heating and restored by X-ray irradiation.

Field identification & locations

Identify in the field by its hardness (will scratch glass), lack of cleavage, and smoky translucent color. Often found in granite pockets. Major sources include Brazil, Switzerland, and the United States (Colorado).