mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Gray to brownish-black translucent, Luster: Vitreous, Crystal structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified May 12, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Gray to brownish-black translucent, Luster: Vitreous, Crystal structure: Hexagonal (trigonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Forms in igneous and metamorphic rocks, especially pegmatites and hydrothermal veins. The smoky color is caused by natural irradiation of aluminum impurities within the crystal lattice.

Uses & applications

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

Geological facts

Smoky quartz is the national gem of Scotland, where it is often called 'Cairngorm' after the mountains where it is found. It was used in China for the earliest sunglasses in the 12th century.

Field identification & locations

Identify in the field by its hardness (scratches glass), lack of cleavage, and translucent smoky appearance. Commonly found in Brazil, USA (Colorado), Switzerland, and Scotland.