mineral

Smoky Quartz

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Brownish gray to black, Luster: Vitreous (glassy), Crystal structure: Hexagonal/Trigonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Identified April 9, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish gray to black, Luster: Vitreous (glassy), Crystal structure: Hexagonal/Trigonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Formation & geological history

Formed in igneous rocks like pegmatites and granites through hydrothermal processes. The smoky color is caused by natural gamma radiation from the surrounding rock acting on trace aluminum impurities within the crystal lattice.

Uses & applications

Used in gemstone jewelry, ornamental carvings, and historical optical instruments (early sunglasses in China). Frequently used in metaphysical and spiritual practices. High-quality pieces are for mineral collecting.

Geological facts

Smoky quartz is the national gemstone of Scotland, where it is known as 'Cairngorm'. Some specimens can reach massive sizes weighing several tons in specific pegmatite caves.

Field identification & locations

Identify in the field by its distinct smoky transparency, conchoidal (shell-like) fracture pattern, and ability to scratch glass. It is commonly found in mountainous regions such as the Swiss Alps, Brazil, and the United States (Colorado).