mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Ranges from light translucent grey to deep brownish-black; Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Ranges from light translucent grey to deep brownish-black
Luster: Vitreous (glassy)

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydro-thermal veins. The distinctive color is caused by natural irradiation of aluminum impurities within the crystal lattice over millions of years.

Uses & applications

Commonly used in jewelry (faceting and beads), ornamental carvings, and by crystal collectors for aesthetic value. Historically used in China for early sunglasses in the 12th century.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountains where it is found. Deeply dark, opaque varieties are specifically referred to as 'Morion'.

Field identification & locations

Identify by its smoky translucence, hexagonal prismatic shape with pyramidal terminations, and its ability to scratch glass. Common locations include Brazil, Madagascar, Switzerland, and the USA (Colorado).