mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Brownish-gray to black, Luster: Vitreous (glassy), Crystal Structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified July 5, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish-gray to black, Luster: Vitreous (glassy), Crystal Structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed in igneous rocks like granite and pegmatites, as well as metamorphic rocks. The smoky color is caused by natural irradiation of aluminum-bearing quartz. Most specimens are from the Phanerozoic eon.

Uses & applications

Used widely in jewelry, ornamental carvings, and by crystal collectors. Occasionally used in electrical components, though clear quartz is preferred.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as Cairngorm. The darkest, nearly opaque variety is called Morion.

Field identification & locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent brown tone. Commonly found in Brazil, Switzerland, and the USA (Colorado). Collectors look for well-defined hexagonal terminations.