sedimentary

Chert (Jasper) Pebble

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: reddish-brown, tan, and grey; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture).

Hardness: 7 Mohs
Color: reddish-brown, tan, and grey
Luster: dull to waxy

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: reddish-brown, tan, and grey; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture).

Formation & geological history

Forms via the precipitation of silica in sedimentary environments, often associated with marine deposits or terrestrial groundwater movement through limestone or volcanic ash. This specimen appears water-worn.

Uses & applications

Mainly used as decorative gravel, in landscaping, or as tumbled stones for hobbyist collections. Historically used for stone tools due to its sharp fracture edges.

Geological facts

Chert is so durable that it often survives long-distance transport in rivers and along beaches, which is why it is often found as smooth, rounded pebbles far from its source rock.

Field identification & locations

Identify by its high hardness (scratches glass), smooth texture, and smooth curved (conchoidal) fractures if broken. Common on riverbeds and coastal beaches worldwide.