sedimentary

Possible weathered chert or flint pebble

Microcrystalline quartz (SiO₂), possibly chalcedony-rich chert

AI-generated identification · may be incorrect

Gray, rounded, dull-to-waxy luster with pale mottling; likely hardness about 6.5–7, no obvious cleavage, and conchoidal fracture if freshly broken. The surface appears strongly weathered or coated, making texture and color uncertain.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica-rich groundwater replaces or fills sediment, commonly in limestone or marine sedimentary rocks; formation ages range from Precambrian to recent. This rounded specimen was likely shaped by stream or beach transport.

Uses & applications

Common chert is used locally for aggregate, road material, and historically for tools and fire-starting; attractive pieces may be collected but are rarely used as gemstones.

Geological facts

Chert and flint are chemically similar varieties of microcrystalline quartz; flint is typically dark and associated with chalk. A fresh edge can produce a sharp conchoidal fracture and, against steel, sometimes sparks.

Field identification & locations

Likely locations include limestone terrains, river gravels, beaches, and glacial deposits. Confirm by testing a hidden area for glass-like fracture and inability to scratch it with a steel knife; avoid destructive testing if valuable.