What's That Rock?Chert
Also called: flint
A hard, fine-grained rock made of microscopic quartz. Flint is a dark kind found in chalk and was used for early tools and fire starting.
Safety
Broken edges are very sharp.
How to identify Chert
- Hard: scratches glass
- Breaks with sharp, shell-like curved surfaces
- Dull to waxy and fine-grained
Often confused with
Is Chert valuable?
Inexpensive.
What changes the price
- Common rock: low value as a specimen
- Flint with good color or knapping quality is worth more to toolmakers
- Artifacts made of chert are valued as artifacts, not as the stone
Uses
- Early stone tools, flint and steel fire starting
Care
Edges can be sharp.
Identifying a stone from a description or a photo is an estimate. Many stones look alike. Ask an expert or a gem lab before you buy, sell or rely on an identification.
Updated October 2026