mineral

Smoky Quartz

Silicon Dioxide (SiO2) with aluminum impurities

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown to black, smoky gray; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brown to black, smoky gray
Luster: Vitreous (glassy)

Identified May 25, 2026More mineral →

Explore Smoky Quartz in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Brown to black, smoky gray; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Formation & geological history

Forms in igneous rocks like granite and in metamorphic rocks through hydrothermal processes. The color results from natural radiation acting on aluminum impurities within the crystal lattice.

Uses & applications

Used in gemstone jewelry, ornamental carvings, and as a popular collector's mineral. Occasionally used in electronics for its piezoelectric properties if high purity.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as Cairngorm after the mountain range where it was historically found.

Field identification & locations

Identify in the field by its hardness (will scratch glass), translucent smoke-like color, and lack of well-defined cleavage. Commonly found in Brazil, USA (Colorado), and Switzerland.