mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

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

Identified July 18, 2026More mineral →

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Physical properties

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

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.

Uses & applications

Used extensively in jewelry (as gemstones), decorative carvings, and as a popular specimen for mineral collectors. Some industrial use in electronics, though synthetic quartz is more common there.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm'. In ancient China, it was used to create the first sunglasses to hide the wearer's facial expressions in court.

Field identification & locations

Identified by its distinctive smoky translucency and hardness (it will scratch glass). It is commonly found in mountain ranges such as the Alps, Brazil, and the United States (Colorado).