mineral
Smoky Quartz
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale; Color ranges from light brownish-gray to deep dark brown or black; Luster is vitreous (glassy); Crystal structure is trigonal; Cleavage is absent; Specific gravity is approximately 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; Color ranges from light brownish-gray to deep dark brown or black; Luster is vitreous (glassy); Crystal structure is trigonal; Cleavage is absent; Specific gravity is approximately 2.65.
Formation & geological history
Formed in hydrothermal veins and igneous environments such as pegmatites and granites, where natural radiation from surrounding radioactive rocks alters the silicon dioxide lattice.
Uses & applications
Commonly used in jewelry, lapidary arts, decorative carvings, and as a popular mineral specimen for collectors.
Geological facts
The dark color is caused by free silicon formed from silicon dioxide by natural irradiation. It is the national gemstone of Scotland.
Field identification & locations
Identified by its distinctive brown-to-gray translucent coloration, conchoidal fracture, and high scratch resistance (hardness 7). Found worldwide, with notable deposits in Brazil, Switzerland, and the United States.
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