mineral

Smoky Quartz and Clear Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Ranges from transparent/colorless to brownish-grey (smoky); Luster: Vitreous (glass-like); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Ranges from transparent/colorless to brownish-grey (smoky)
Luster: Vitreous (glass-like)

Identified March 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the crystallization of silica-rich hydrothermal fluids or cooling magma in cavities (vugs) within igneous or metamorphic rocks. The smoky hue is caused by natural gamma irradiation of trace aluminum impurities over millions of years.

Uses & applications

Extensively used in jewelry (faceting and cabochons), ornamental decor, and as popular specimens for mineral collectors. Industrially, quartz is used in electronics for its piezoelectric properties and in glass making.

Geological facts

Quartz is one of the most abundant minerals in Earth's crust. Smoky quartz is the national gem of Scotland, where it is known as 'Cairngorm' after the mountain range where it was historically mined.

Field identification & locations

Identify in the field by its characteristic point-terminated hexagonal crystals, lack of cleavage, and ability to scratch glass. Commonly found in Brazil, Madagascar, the Swiss Alps, and several locations across the United States (like Colorado and Arkansas).

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