sedimentary

Yellow-brown chert or silicified rock

Microcrystalline quartz (SiO₂), possibly iron-stained chert

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, dull to waxy luster, opaque yellow-brown color, and no visible cleavage; the rounded surface appears naturally weathered or tumbled. Exact identification is limited by the photograph and lack of a fresh edge or tests.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica from biological remains or groundwater replaces sediment, commonly in limestone or marine sedimentary layers. Its age varies widely from Precambrian to recent; iron oxides create the ochre coloration.

Uses & applications

Used historically for sharp-edged tools and occasionally as aggregate or decorative stone; ordinary pieces have little jewelry value.

Geological facts

A fresh fracture should be smooth, curved (conchoidal), and glassy rather than granular. It may resemble jasper, but jasper is generally more vividly colored and opaque.

Field identification & locations

Common in sedimentary terrains, including limestone regions and gravel deposits worldwide. Test with a steel file or quartz: it should resist scratching by steel and may scratch ordinary glass; avoid damaging collectible specimens.