mineral

Smoky Quartz

Smoky Quartz (SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey, black, or translucent smoke-color; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brownish-grey, black, or translucent smoke-color
Luster: Vitreous (glassy)

Identified April 26, 2026More mineral →

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Physical properties

Formation & geological history

Forms in igneous rocks like graniites and pegmatites. The smoky color is caused by natural irradiation of trace aluminum impurities within the crystal lattice over long periods of geological time.

Uses & applications

Used primarily in lapidary work for jewelry, gemstone carving, and popular as metaphysical/collecting specimens. Occasionally used in optical instruments.

Geological facts

The color can be artificially induced by laboratory irradiation. Historical 'sunglasses' in 12th century China were made using flat panes of smoky quartz.

Field identification & locations

Identify by its hardness (scratches glass), lack of cleavage, and the characteristic conchoidal fracture (curved, shell-like breaks). Common in river beds downstream from granitic mountains.