mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Hardness: 7 (Mohs scale); Color: Brownish-grey, black, or smoky translucent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Brownish-grey, black, or smoky translucent
Luster: Vitreous (glassy)

Identified June 15, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: Brownish-grey, black, or smoky translucent; Luster: Vitreous (glassy); Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed in igneous or metamorphic rocks like granite or gneiss. It acquires its smoky color through natural irradiation of trace aluminum impurities over millions of years.

Uses & applications

Used in gemstone jewelry, ornamental carvings, and historical optical instruments. It is also a very popular specimen for mineral collectors.

Geological facts

Smoky quartz is the national gem of Scotland, where it is often referred to as 'Cairngorm'. Its dark color is a result of free silicon, formed from the silicon dioxide by natural radiation.

Field identification & locations

Identify by its translucent brownish tint and glassy fracture surfaces. It is typically found in pegmatite dikes and alpine-type fissures globally, especially in Brazil and the USA.