mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Grayish-brown to black, translucent to nearly opaque; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

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

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly granite pegmatites. The smoky color is caused by natural irradiation of aluminum-bearing quartz over millions of years. It occurs in rocks ranging from Precambrian to more recent geological eras.

Uses & applications

Used primarily in jewelry (as faceted stones), decorative ornaments, and metaphysical collecting. Historically used for making early sunglasses in China and in glass manufacturing.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm.' Large crystals can grow to weigh hundreds of pounds in ideal pegmatite environments.

Field identification & locations

Identify in the field by its six-sided crystal habit, lack of cleavage, and its ability to scratch glass. It is commonly found in Brazil, Madagascar, the Swiss Alps, and the United States (notably Colorado and New Hampshire).