mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Translucent grey to brownish-black
Luster: Vitreous

Identified March 11, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Translucent grey to brownish-black; Luster: Vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed in igneous or metamorphic rocks, specifically pegmatites. The smoky color is caused by natural irradiation of aluminum-bearing quartz over geological time scales, typically occurring in environments rich in radioactive elements like uranium or thorium.

Uses & applications

Used primarily in jewelry as a gemstone, in lapidary arts for carvings and tumbled stones, and as an ornamental decorative mineral. Historically used in early sundial lenses and optical equipment.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm.' Some of the darkest varieties are called 'Morion.' While natural irradiation is common, much of the very dark material on the market is clear quartz that has been artificially irradiated.

Field identification & locations

Identify in the field by its hardness (will scratch glass), translucent character, and lack of cleavage planes. Commonly found in Brazil, Madagascar, the Swiss Alps, and Pikes Peak, Colorado. Collectors should look for uniform color and internal clarity.