sedimentary

Banded Chert

Microcrystalline silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Gray, tan, white, and translucent bands; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Gray, tan, white, and translucent bands
Luster: Waxy to vitreous

Identified March 5, 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

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater. Banding often results from rhythmic deposition or changes in oxidation states during diagenesis in marine or lacustrine environments.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp edges. Modernly used in geological research, as decorative landscaping stone, and occasionally in lapidary work for cabochons.

Geological facts

Chert is so durable it often survives long after the surrounding rock has eroded away. It was one of the most vital materials for prehistoric humans to create fire-starting kits and hunting tools.

Field identification & locations

Identify by its 'flint-like' waxy texture, sharp edges when broken, and inability to be scratched by a steel knife. Commonly found in limestone or chalk beds as nodules or distinct layers. Collectors should look for unique banding patterns.