sedimentary

Chert (and Flint variant)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: White, tan, or grey with possible banding. Luster: Dull to waxy. Structure: Microcrystalline quartz (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: White, tan, or grey with possible banding
Luster: Dull to waxy

Identified March 29, 2026More sedimentary →

Explore Chert (and Flint variant) 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 radiolarians or sponges) or by chemical precipitation from groundwater within limestone or chalk beds. Most common in Paleozoic and Mesozoic rock layers.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used as road aggregate, in glass manufacturing, and as decorative gravel.

Geological facts

Chert is so hard it can produce sparks when struck against steel. It was one of the most important minerals for prehistoric humans to create arrowheads, spear tips, and scrapers.

Field identification & locations

Identify by its 'conchoidal' (shell-like) fracture patterns and ability to scratch glass. It is often found as nodules inside limestone cliffs or as rounded pebbles in riverbeds. It feels smooth and 'sharp' on the edges.