mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Grayish-brown to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grayish-brown to black
Luster: Vitreous (glassy)

Identified May 2, 2026More mineral →

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: Grayish-brown to black; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: Indistinct; Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, especially pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of aluminum impurities within the crystal structure.

Uses & applications

Used in jewelry (gemstones), electronics (piezoelectric applications), and is highly valued by mineral collectors for its metaphysical properties and aesthetic appeal.

Geological facts

Cairngorm is a famous variety of smoky quartz found in the Cairngorm Mountains of Scotland. It is the national gemstone of Scotland and has been used for centuries in Highland traditional dress.

Field identification & locations

Identify by its smoky transparency and crystal habit. It is often found in mountainous regions such as the Swiss Alps, Brazil, and the United States (Colorado). Collectors look for well-defined terminations and deep, uniform color.