mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Ranges from translucent light grey to brownish-black; Luster: Vitreous (glass-like); Crystal structure: Trigonal/Hexagonal prisms; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Ranges from translucent light grey to brownish-black
Luster: Vitreous (glass-like)

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic rocks (especially pegmatites) through the slow cooling of silica-rich fluids. The dark color is caused by natural irradiation of trace aluminum impurities within the crystal lattice.

Uses & applications

Commonly used in jewelry (faceting and beads), ornamental carvings, and electronics due to its piezoelectric properties. It is also an extremely popular item for mineral collectors.

Geological facts

The dark color is not inherent but is caused by gamma rays from surrounding radioactive rocks altering the quartz structure. When heated, smoky quartz can turn yellow and be sold as 'burnt' citrine.

Field identification & locations

Identify in the field by its distinct smoky transparency, lack of cleavage, and ability to scratch glass. Commonly found in Brazil, Switzerland, and the United States (Colorado). Look for hexagonal crystal points with horizontal striations on facets.