mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

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

Identified March 29, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites. The distinctive smoky color is caused by natural irradiation of aluminum-bearing quartz crystals over millions of years within the Earth's crust.

Uses & applications

Commonly used in jewelry (faceting and beads), metaphysical purposes, and as a popular mineral specimen for collectors. In industry, quartz is used for its piezoelectric properties and in glass making.

Geological facts

Smoky Quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the Cairngorm Mountains. The darkest, almost opaque variety is often called 'Morion'.

Field identification & locations

Identify in the field by its smoky transparency, lack of cleavage, and the ability to scratch glass. It is commonly found in Brazil, Madagascar, the United States (Colorado and New Hampshire), and the Swiss Alps.