mineral
Smoky Quartz
Silicon dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: light grayish-brown to dark black; Luster: vitreous (glassy); Crystal structure: trigonal; Cleavage: none; Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- light grayish-brown to dark black
- Luster
- vitreous (glassy)
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Physical properties
Hardness: 7 (Mohs scale); Color: light grayish-brown to dark black; Luster: vitreous (glassy); Crystal structure: trigonal; Cleavage: none; Specific gravity: 2.65
Formation & geological history
Formed in igneous, metamorphic, and sedimentary rocks. Its color is due to free silicon formed from the silicon dioxide by natural irradiation.
Uses & applications
Commonly used in jewelry, decorative items, and for collecting.
Geological facts
Smoky quartz is the national gem of Scotland. It is often found with rutile inclusions.
Field identification & locations
Identify by its smoky brown to black color and typical quartz hardness. Commonly found in Brazil, Madagascar, the United States, and the Swiss Alps.
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sedimentary
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Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
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Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
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