mineral

Smoky Quartz

Silicon Dioxide (SiO2)

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

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

Identified June 28, 2026More mineral →

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Physical properties

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

Formation & geological history

Forms in igneous and metamorphic rocks, particularly granite pegmatites and hydrothermal veins. Color is caused by natural irradiation of aluminum-containing quartz over millions of years.

Uses & applications

Used widely in jewelry (gemstones), ornamental carvings, crystal healing practices, and as a collector specimen. Historically used for making early sunglasses in China.

Geological facts

The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. It is the national gem of Scotland, where it is often referred to as Cairngorm after the mountain range.

Field identification & locations

Identify by its smoky translucence and hardness (it will scratch glass). Commonly found in Brazil, Madagascar, the Swiss Alps, and the United States (Colorado).