mineral
Tumbled jasper or weathered chert
Microcrystalline quartz (SiO₂), likely jasper/chert with iron-oxide impurities
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque tan, brown, and reddish mottling; dull to weakly waxy luster; cryptocrystalline structure with no visible cleavage. The rounded shape and smooth surface indicate natural water wear or tumbling.
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Physical properties
Hardness about 6.5–7 Mohs; opaque tan, brown, and reddish mottling; dull to weakly waxy luster; cryptocrystalline structure with no visible cleavage. The rounded shape and smooth surface indicate natural water wear or tumbling.
Formation & geological history
Forms when silica-rich groundwater replaces or fills sediment, producing microcrystalline quartz; red-brown colors come from hematite or limonite. Precise age and locality cannot be determined from the photograph.
Uses & applications
Used as ornamental stone, beads, cabochons, carvings, and lapidary material; common pieces have modest collecting value.
Geological facts
Jasper is an opaque variety of chalcedony, while chert is the broader rock term for microcrystalline quartz. Color patterns and hardness are more diagnostic than surface shape.
Field identification & locations
Common in river gravels and silica-rich sedimentary formations worldwide, especially areas with volcanic ash or iron-rich sediments. Scratch testing with a steel file or glass, combined with a nonmetallic streak and absence of fizz in dilute acid, helps distinguish it from softer rocks.
