What's That Rock?Coal
A black, burnable sedimentary rock made from ancient plant remains. Hardness and shine rise from soft lignite to hard, shiny anthracite.
Safety
Coal dust is harmful to breathe and coal can burn. Do not burn it indoors.
How to identify Coal
- Light for a black rock
- Soft and brittle, leaves black marks
- Plant fossils (leaves, bark) can show on its layers
Often confused with
Is Coal valuable?
Inexpensive.
What changes the price
- Common material: very low value as a specimen
- Anthracite and jet-like coals can be carved, but the price is small
- It is mostly a fuel and an educational specimen
Uses
- Fuel and steelmaking
Care
Dusty and crumbly.
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