mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey to black; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

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

Identified March 9, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brownish-grey to black; Luster: Vitreous; Crystal Structure: Hexagonal (Trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, specifically pegmatites and hydrothermal veins. The color is caused by natural irradiation acting on traces of aluminum within the crystal lattice.

Uses & applications

Used in jewelry (gemstones), ornamental carvings, crystal healing, and as a component in oscillators for electronics (though synthetic quartz is more common for technology).

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the Cairngorm Mountains. It was used in China as early as the 12th century to make the first recorded sunglasses.

Field identification & locations

Identify in the field by its hexagonal prism shape, lack of cleavage (conchoidal fracture), and translucent to transparent 'smoke' color. Found worldwide, with major deposits in Brazil, Switzerland, and the USA.