sedimentary

Banded Chert

Silicon dioxide (SiO2) with impurities

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Tan, brown, green, and cream; Luster: Waxy to dull; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.8

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

Identified July 15, 2026More sedimentary →

Explore Banded Chert in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, green, and cream; Luster: Waxy to dull; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.8

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, followed by lithification over millions of years. Banding often occurs due to rhythmic changes in sediment supply.

Uses & applications

Primarily collected as display specimens or lapidary material. Historically used for stone tools (arrowheads, scrapers) due to its sharp conchoidal fracture.

Geological facts

This specimen is a river-worn pebble where the banding has been exposed and smoothed by water action. Similar stones with distinctive patterns are sometimes called 'concretionary chert' or 'river jasper' by collectors.

Field identification & locations

Identify in the field by its waxy texture, inability to be scratched by a steel knife, and characteristic 'bulla' or concentric banding. Often found in riverbeds or coastal gravels.