sedimentary

Banded Chert

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, grey, and brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal; Cleavage: None

Hardness: 7 on Mohs scale
Color: Tan, beige, grey, and brown
Luster: Waxy to dull

Identified July 20, 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: 7 on Mohs scale; Color: Tan, beige, grey, and brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal; Cleavage: None

Formation & geological history

Formed by the accumulation and lithification of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from hydrothermal fluids in marine environments. Often found as nodules or layers within limestone.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to conchoidal fracture. Currently used as road surfacing material, in construction, and as decorative landscape stones.

Geological facts

Chert is so hard it can scratch steel and was used for centuries as a 'flint' to start fires. The banding represents changes in sediment deposition or mineral impurities over time.

Field identification & locations

Identify in the field by its waxy texture and sharp, shell-like (conchoidal) fracture patterns when broken. Common in limestone belts and riverbeds in the Midwestern USA and Europe.