mineral
Tumbled brown-and-cream stone, likely jasper or chert
Microcrystalline quartz (SiO₂), probably jasper/chert; exact identification requires testing
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque brown, cream, and gray mottling with a smooth tumbled surface and dull to waxy luster. Quartz has a trigonal crystal structure, but the microscopic grains show no visible cleavage.
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Physical properties
Hardness about 6.5–7 Mohs; opaque brown, cream, and gray mottling with a smooth tumbled surface and dull to waxy luster. Quartz has a trigonal crystal structure, but the microscopic grains show no visible cleavage.
Formation & geological history
Formed from silica-rich fluids or sediment that lithified and recrystallized into microcrystalline quartz, likely millions to hundreds of millions of years old; subsequently shaped by tumbling. Common sources include sedimentary terrains worldwide.
Uses & applications
Used as a lapidary stone for beads, cabochons, carvings, and decorative objects; less commonly used as crushed aggregate. Modest specimens are primarily collectible or ornamental.
Geological facts
Jasper is an opaque variety of chalcedony, while chert is typically silica-rich sedimentary rock; the boundary can be difficult to determine visually. The specimen’s rounded, polished form indicates human processing.
Field identification & locations
Identify with a scratch test: it should scratch ordinary glass but not be scratched by a steel knife; it should not fizz in dilute acid. Commonly sold as tumbled jasper, chert, or “picture jasper.”
