sedimentary

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely iron-stained chert/jasper

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, opaque brown to reddish-brown color, waxy to glassy luster, very fine-grained cryptocrystalline structure, and no visible cleavage. The rounded, glossy surface indicates natural water wear or tumbling/polishing.

Identified September 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich fluids replace or precipitate from sediment, commonly in limestone or marine sediments; iron oxides create the brown coloration. Its exact geological age cannot be determined from the photograph.

Uses & applications

Used as decorative stone, lapidary material, cabochons, beads, and occasionally as a durable aggregate or toolstone. This specimen appears primarily ornamental or collectible.

Geological facts

Chert fractures conchoidally and can produce extremely sharp edges when broken. Jasper is an opaque, impure variety of chert containing iron oxides and other minerals.

Field identification & locations

Identify with a steel scratch test (it should resist scratching), absence of cleavage, and conchoidal fracture; a streak test is usually white to pale brown. Common sources include river gravels and sedimentary regions worldwide.