metamorphic
Tumbled quartz-rich stone, possibly quartzite or agate
Quartz (SiO₂), likely in a quartzite or chalcedony-rich matrix
AI-generated identification · may be incorrectSmall polished/tumbled specimen with white to gray translucent areas and brown iron-oxide staining; vitreous to waxy luster, no obvious cleavage, and likely Mohs hardness around 7. Crystal structure is trigonal for quartz; specific gravity is about 2.65.
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Physical properties
Small polished/tumbled specimen with white to gray translucent areas and brown iron-oxide staining; vitreous to waxy luster, no obvious cleavage, and likely Mohs hardness around 7. Crystal structure is trigonal for quartz; specific gravity is about 2.65.
Formation & geological history
Quartzite forms when quartz sandstone is metamorphosed under heat and pressure; chalcedony/agate forms from silica-rich fluids filling cavities. The exact geological age and locality cannot be determined from the photograph.
Uses & applications
Suitable for decorative stone, cabochons, tumbled-stone collections, and craft jewelry; quartzite is also used as aggregate and durable building stone. This small piece has mainly ornamental value.
Geological facts
The brown coloration is probably limonite or hematite staining, while the pale translucent material is quartz or chalcedony. Polishing can obscure original grain, banding, and crystal boundaries.
Field identification & locations
Test cautiously with a steel file or glass: quartz-rich material should scratch glass and resist a steel blade. Common sources include Brazil, Madagascar, India, and the western United States; locality-specific identification requires testing or provenance.
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