mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Brownish gray to translucent black, Luster: Vitreous, Crystal System: Hexagonal (Trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish gray to translucent black, Luster: Vitreous, Crystal System: Hexagonal (Trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation acting on aluminum impurities within the quartz lattice.

Uses & applications

Used in jewelry as gemstones, architectural ornamentation, and as a popular specimen for mineral collectors. Historically used for ancient 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. The coloring can be dark enough to be nearly opaque, a variety known as morion.

Field identification & locations

Identify in the field by its hardness (will scratch glass), lack of cleavage, and translucent brown to gray hue. It is commonly found globally, notably in Brazil, Madagascar, and the Swiss Alps.