metamorphic
Polished/tumbled quartz-rich rock, possibly quartzite
Quartzite; predominantly crystalline SiO₂, with minor iron-oxide and other impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; rounded and heavily polished, with gray-tan coloration, white translucent quartz patches, earthy inclusions, and a vitreous to waxy luster. Quartzite has interlocking quartz grains and no prominent cleavage; specific gravity is approximately 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; rounded and heavily polished, with gray-tan coloration, white translucent quartz patches, earthy inclusions, and a vitreous to waxy luster. Quartzite has interlocking quartz grains and no prominent cleavage; specific gravity is approximately 2.6–2.7.
Formation & geological history
Likely formed when quartz-rich sandstone recrystallized under heat and pressure during regional metamorphism, then was naturally or mechanically rounded and polished. Its exact geological age cannot be determined from the image.
Uses & applications
Suitable as a decorative stone, paperweight, carving, or lapidary specimen; quartzite is also used as aggregate, building stone, and occasionally countertops. This rounded piece has modest collector value unless provenance or unusual mineralization is documented.
Geological facts
The white areas are likely quartz-rich zones, while the darker tan-gray material may contain iron oxides or mica. Its extreme hardness should allow it to scratch ordinary glass.
Field identification & locations
Confirm with a glass-scratch test and inspect a fresh edge for interlocking quartz grains; it should not fizz with dilute hydrochloric acid. Common sources include metamorphic belts worldwide, especially Brazil, India, Scandinavia, and the United States.
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