mineral

Tumbled jasper or weathered chert

Microcrystalline quartz (SiO₂), likely jasper/chert with iron-oxide impurities

AI-generated identification · may be incorrect

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.

Identified August 25, 2026More mineral →

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Physical properties

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.