mineral
Smoky quartz crystal fragment
Quartz (SiO₂), smoky variety
AI-generated identification · may be incorrectTranslucent gray-brown with a vitreous luster and irregular fracture; quartz has Mohs hardness 7, a trigonal crystal structure, no cleavage, and specific gravity about 2.65. The image shows a small rough fragment, so crystal habit and exact identification are not certain.
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Physical properties
Translucent gray-brown with a vitreous luster and irregular fracture; quartz has Mohs hardness 7, a trigonal crystal structure, no cleavage, and specific gravity about 2.65. The image shows a small rough fragment, so crystal habit and exact identification are not certain.
Formation & geological history
Forms when trace natural irradiation colors quartz in silica-rich igneous or metamorphic rocks and hydrothermal veins; deposits range from ancient to geologically recent.
Uses & applications
Used as a collector specimen and, when clear and attractive, in jewelry; quartz also has broad industrial uses in glass and electronics.
Geological facts
Smoky coloration results from irradiation acting on trace aluminum impurities in quartz.
Field identification & locations
Look for glassy luster, hardness sufficient to scratch glass, and lack of cleavage; common localities include Brazil, the Alps, and the United States. Small rough fragments typically sell for about $2–$20 USD.
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