Rock Identifier
Smoky Quartz (with possible Feldspar inclusions) (Silicon Dioxide (SiO2)) — mineral
mineral

Smoky Quartz (with possible Feldspar inclusions)

Silicon Dioxide (SiO2)

Hardness: 7.0 on Mohs scale; Color: Grayish-brown, smoky, translucent to opaque; Luster: Vitreous to greasy (when weathered); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65.

Hardness
7
Color
Grayish-brown, smoky, translucent to opaque
Luster
Vitreous to greasy (when weathered)
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Physical properties

Hardness: 7.0 on Mohs scale; Color: Grayish-brown, smoky, translucent to opaque; Luster: Vitreous to greasy (when weathered); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through the natural irradiation of aluminum-containing rock crystal (quartz) within igneous or metamorphic environments, most commonly in pegmatites. It forms deep within the earth's crust under high pressure and temperature over millions of years.

Uses & applications

Used in the gemstone and jewelry industry when high clarity is present. Lower grade specimens are used in lapidary work for decorative objects, or as healing crystals in the metaphysical market.

Geological facts

The 'smoky' color is caused by free silicon formed from the silicon dioxide by natural irradiation. It is the national gem of Scotland, where it is known as 'Cairngorm' after the Cairngorm Mountains.

Field identification & locations

Identify in the field by its hardness (it should scratch glass but not be scratched by a steel file), lack of cleavage, and translucent 'root beer' or gray color. Commonly found in granite-rich regions and alluvial deposits.

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