mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale). Color: Brownish-gray to black. Luster: Vitreous (glassy). Crystal structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

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

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale). Color: Brownish-gray to black. Luster: Vitreous (glassy). Crystal structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Formation & geological history

Formed in igneous rocks like granite or metamorphic rocks. The smoky color occurs when natural radiation from the surrounding rock acts upon trace amounts of aluminum within the crystal lattice, often over millions of years spanning from the Precambrian to Cenozoic eras.

Uses & applications

Commonly used in jewelry as faceted stones or beads, as ornamental carvings, and widely collected by mineral enthusiasts. In industry, quartz is used for its piezoelectric properties in electronics, though clear quartz is preferred.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. In ancient China, it was used to create the first vision-correcting lenses for sunglasses. Dark, opaque specimens are often referred to as 'Morion'.

Field identification & locations

Identify in the field by its characteristic six-sided prism shape terminating in a pyramid, its hardness (it can scratch glass), and its smoky translucency. Common locations include the Swiss Alps, Brazil, Madagascar, and the Pikes Peak region of Colorado, USA.