mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey, smoky, to nearly black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brownish-grey, smoky, to nearly black
Luster: Vitreous

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brownish-grey, smoky, to nearly black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Forms in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of aluminum impurities within the crystal lattice.

Uses & applications

Used primarily in jewelry (faceting), carvings, and ornamental displays. Historically used in early optical lenses and remains a favorite for mineral collectors.

Geological facts

Smoky Quartz is the national gemstone of Scotland, where it is known as 'Cairngorm.' Some of the darkest varieties are called 'Morion.' It is often found as massive crystals that can weigh hundreds of pounds.

Field identification & locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent smoky color. Common in mountainous regions like the Alps, Brazil, and the United States (Colorado).