mineral
Tumbled quartz crystal (likely smoky or iron-stained quartz)
Quartz, silicon dioxide (SiO₂)
AI-generated identification · may be incorrectHardness 7 Mohs; translucent brown-gray color with a vitreous luster and irregular conchoidal fracture. Quartz is trigonal, lacks cleavage, and has a specific gravity of about 2.65.
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Physical properties
Hardness 7 Mohs; translucent brown-gray color with a vitreous luster and irregular conchoidal fracture. Quartz is trigonal, lacks cleavage, and has a specific gravity of about 2.65.
Formation & geological history
Forms when silica-rich fluids crystallize in cavities and veins, commonly in igneous and metamorphic environments; the specimen has been naturally or artificially rounded by tumbling. Quartz ranges from Precambrian to recent in age.
Uses & applications
Used for abrasives, glass, electronics, and ornamental stone; small tumbled pieces typically have little commercial value.
Geological facts
The brown color may reflect natural smoky coloration from radiation-related defects or iron staining/inclusions. The photograph alone cannot distinguish smoky quartz from stained or included clear quartz with certainty.
Field identification & locations
Common worldwide, especially in Brazil, Madagascar, the United States, and alpine or hydrothermal veins. A glass-scratch test can support identification, though it may damage the specimen; quartz generally scratches glass.
