mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

Hardness: 7 on Mohs scale
Color: Translucent gray to brownish-black
Luster: Vitreous (glassy)

Identified July 4, 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: Translucent gray to brownish-black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites. The smoky color is caused by natural irradiation of aluminum-bearing quartz over millions of years within the earth's crust.

Uses & applications

Used extensively in jewelry, ornamental carvings, and as a popular collector's mineral. Historically used in early pince-nez sunglasses in China.

Geological facts

The national gem of Scotland, where it is often referred to as 'Cairngorm' after the mountains where it is found. Its color can range from a light 'whiskey' brown to a nearly opaque 'Morion' black.

Field identification & locations

Identify by its characteristic smoky transparency, lack of cleavage, and ability to scratch glass. Commonly found in Brazil, Madagascar, the Swiss Alps, and the United States (Colorado).