sedimentary

Tumbled jasper or chert pebble

Microcrystalline quartz (SiO₂), likely opaque chalcedony/jasper or chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; rounded, gray-brown to tan, opaque, with a dull to slightly waxy luster. Microcrystalline quartz has no visible cleavage and conchoidal fracture; specific gravity is approximately 2.6.

Identified August 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids replaced or cemented sediment, producing dense microcrystalline quartz; later weathering and stream transport rounded the specimen. The geological age cannot be determined from the photograph and may range from ancient to relatively young.

Uses & applications

Used as decorative stone, lapidary material, tumbled stone, and occasionally for minor carvings or tools; this specimen has modest jewelry and display value.

Geological facts

The pale patches may represent quartz-rich zones, weathering, or remnants of host sediment. Chert and jasper are distinguished mainly by texture and color: jasper is commonly iron-stained and opaque, while chert is often gray or brown.

Field identification & locations

Look for a glassy or waxy surface, conchoidal chips, absence of large crystals, and the inability to scratch it with a steel knife. Common in river gravels and silica-rich sedimentary formations worldwide; acid causes no reaction.