mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Hardness: 7 (Mohs scale); Color: Translucent brown, gray, to black; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Translucent brown, gray, to black
Luster: Vitreous

Identified June 28, 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 (Mohs scale); Color: Translucent brown, gray, to black; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in igneous or metamorphic rocks like granite or pegmatites. The smoky color results from natural irradiation of aluminum-bearing quartz over long geological periods.

Uses & applications

Used widely in jewelry as a gemstone, in decorative carvings, and in industrial applications for its piezoelectric properties or as an abrasive.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often called 'Cairngorm' after the mountain range where it is frequently discovered.

Field identification & locations

Identify in the field by its pyramidal terminations, lack of cleavage, and vertical striations on crystal faces. Common in mountain ranges with prominent granite outcrops.