mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Brown, black, or smoky gray; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: Indiscernible; Specific Gravity: 2.65

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

Identified June 22, 2026More mineral →

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: Brown, black, or smoky gray; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: Indiscernible; Specific Gravity: 2.65

Formation & geological history

Smoky Quartz is formed in igneous and metamorphic rocks, particularly granite and pegmatites. The smoky color is caused by natural irradiation from surrounding radioactive elements (like uranium or thorium) and the presence of trace aluminum within the crystal lattice. These processes can take millions of years.

Uses & applications

Used extensively in jewelry for rings, pendants, and earrings. It is also a popular collector's mineral and is sometimes used in industrial applications for its piezoelectric properties, though synthetic quartz is more common for high-precision technology.

Geological facts

Smoky Quartz was used in the first sunglasses in 12th century China, where flat panes of the mineral were used to protect judges' eyes so their expressions remained neutral. It is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the mountain range where it was historically mined.

Field identification & locations

Smoky Quartz can be identified in the field by its smoky transparency, lack of cleavage, and ability to scratch glass. It is commonly found in mountainous regions worldwide, including the Swiss Alps, Brazil, Madagascar, and the United States (Colorado). Collectors look for clarity and deep color saturation.