sedimentary

Chert (River Pebble with Liesegang Rings)

Microcrystalline Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and grey. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.5-2.8.

Hardness: 6
Color: Tan, brown, and grey
Luster: Waxy to dull

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and grey. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.5-2.8.

Formation & geological history

Formed via the accumulation of siliceous remains of diatoms or radiolarians, or through chemical precipitation in marine or groundwater environments. Common in Phanerozoic sedimentary sequences.

Uses & applications

Historically used for stone tools and strike-a-lights; currently used in decorative landscaping, as river rock, and as common collector specimens.

Geological facts

The brown patterns are likely Liesegang rings, which are secondary rhythmic chemical precipitates formed during fluid flow through porous rock. Chert is the same material as flint, but usually lighter in color.

Field identification & locations

Identify by its hardness (scratches glass), waxy texture when wet, and smooth, rounded shape if found in rivers or beaches. Very common in outwash plains and riverbeds.