sedimentary

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: multi-toned tan, brown, and grey with a white/pinkish center; Luster: waxy to vitreous; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture)

Hardness: 7 Mohs scale
Color: multi-toned tan, brown, and grey with a white/pinkish center
Luster: waxy to vitreous

Identified July 21, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: multi-toned tan, brown, and grey with a white/pinkish center; Luster: waxy to vitreous; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture)

Formation & geological history

Forms through the accumulation of silica-rich microfossils or chemical precipitation in marine or freshwater environments. This specimen appears water-worn and polished by river or stream action.

Uses & applications

Historically used for making sharp tools and weapons; currently used for decorative garden stones, tumbling, and as a durable construction aggregate.

Geological facts

Chert is one of the most durable sedimentary rocks. When struck against steel, it can create sparks, making it useful for fire-starting in survival situations.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel nail) and smooth, waxy feel. Commonly found in riverbeds, glacial deposits, and as nodules within limestone formations.