mineral
Tumbled smoky quartz (probable)
Quartz, SiO₂; smoky variety colored by irradiation-related defects
AI-generated identification · may be incorrectTranslucent gray-brown to nearly black, vitreous luster, generally massive in this polished form, with no obvious cleavage and conchoidal fracture. Mohs hardness 7; specific gravity about 2.65.
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Physical properties
Translucent gray-brown to nearly black, vitreous luster, generally massive in this polished form, with no obvious cleavage and conchoidal fracture. Mohs hardness 7; specific gravity about 2.65.
Formation & geological history
Forms in silica-rich hydrothermal veins, pegmatites, and cavities in igneous and metamorphic rocks; coloration develops from natural or artificial irradiation of aluminum-bearing quartz. Quartz ranges from Precambrian to modern geological ages.
Uses & applications
Used as a decorative and collecting stone, in jewelry, carvings, and polished specimens; quartz also has major industrial uses in glass, electronics, abrasives, and engineered stone.
Geological facts
The rounded, glossy surface indicates tumbling or polishing, which obscures natural crystal faces and makes exact identification less certain from the image alone.
Field identification & locations
Common sources include Brazil, Madagascar, the United States, Switzerland, and Scotland. Confirm with hardness testing—quartz scratches ordinary glass but should not be scratched by a steel knife—and inspect for glassy fracture and internal veils.
