mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Grayish-brown to black, translucent to opaque; Luster: Vitreous; Crystal Structure: Trigonal (hexagonal prisms); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Grayish-brown to black, translucent to opaque
Luster: Vitreous

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. Its distinct color results from natural gamma radiation (from uranium or thorium in surrounding rock) interacting with trace amounts of aluminum within the crystal lattice.

Uses & applications

Commonly used in jewelry (faceting), crystal healing practices, and as decorative display specimens. Historically used for making the first sunglasses in 12th-century China.

Geological facts

Smoky Quartz from Scotland is famously known as 'Cairngorm' and is the national gemstone of Scotland. While it looks like it's full of smoke, the color is actually due to microscopic structural defects rather than inclusions.

Field identification & locations

Identify in the field by its hexagonal crystal shape, lack of cleavage, and 'smoky' transparency. It is widely found in Brazil, Madagascar, Switzerland (the Alps), and the United States ( Colorado and New Hampshire).