mineral

Smoky Quartz

Smoky Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Grayish-yellow to deep brownish-black; Luster: Vitreous; Crystal structure: Hexagonal/Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grayish-yellow to deep brownish-black
Luster: Vitreous

Identified March 23, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Grayish-yellow to deep brownish-black; Luster: Vitreous; Crystal structure: Hexagonal/Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

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-bearing silicon dioxide during the rock's geological age, often spanning millions of years.

Uses & applications

Commonly used in jewelry as a faceted gemstone (as seen in the image), for ornamental carvings, and in industrial applications for its piezoelectric properties. It is also a popular specimen for mineral collectors.

Geological facts

Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountain range. Historically, the first 'sunglasses' were made in China in the 12th century using flat panes of smoky quartz.

Field identification & locations

Identify by its characteristic 'smoky' translucency and glass-like luster. In the field, look for hexagonal prismatic crystals in granitic pockets. Common locations include Brazil, Madagascar, the Swiss Alps, and the Pikes Peak region of Colorado, USA.