mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Hardness: 7 on Mohs scale. Color: Translucent grey to brownish-black. Luster: Vitreous/glassy. Crystal structure: Hexagonal/Trigonal. Cleavage: Indistinct (conchoidal fracture). Specific Gravity: 2.65.

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

Identified March 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites. The smoky color is caused by natural gamma irradiation from surrounding radioactive elements (like uranium or thorium) affecting aluminum impurities within the crystal lattice during or after formation.

Uses & applications

Used in gemstone jewelry (faceted or cabochon), ornamental carvings, and widely collected as mineral specimens. Historically used for protective talismans and some of the earliest forms of sunglasses in China.

Geological facts

Smoky Quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm' after the Cairngorm Mountains. Very dark, nearly opaque varieties are known as 'Morion'.

Field identification & locations

Identify in the field by its hardness (will scratch glass), glassy luster, and characteristic conchoidal fracture (curved, shell-like breaks). Common in highland regions and granitic terrains globally, including the Swiss Alps, Brazil, and the USA (Colorado).