mineral

Smoky Quartz (Tumbled)

Smoky Quartz (SiO2 - Silicon Dioxide)

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

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

Identified March 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic rocks when clear quartz is exposed to natural gamma radiation from radioactive elements in surrounding rock over millions of years, creating color centers. Found in pegmatites and hydrothermal veins.

Uses & applications

Used primarily in jewelry, lapidary arts (tumbled stones), and as a popular metaphysical or decorative collector's item. In industry, high-purity quartz is used for electronics and optics.

Geological facts

The brown-black smoke-like color is caused by trace amounts of aluminum replacing silicon in the crystal lattice, which then undergoes 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 (scratches glass), conchoidal (shell-like) fracture, and translucent brown tone. Commonly found in Brazil, Madagascar, and the US (Colorado/New Hampshire). This specific specimen is 'tumbled,' meaning it was polished in a machine.

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