What's That Rock?Limestone
A sedimentary rock made mostly of calcite, often from shells and sea life. It may contain visible fossils.
How to identify Limestone
- Fizzes with a drop of vinegar (weakly) or strong acid
- Scratched by a knife easily
- Often contains shells or fossils
Often confused with
- Marblecrystalline, sparkly
- Dolostonefizzes only when powdered
- Chalk
Is Limestone valuable?
Common.
What changes the price
- Common rock: low value as a specimen
- Fossil-rich or decorative polished pieces cost more than plain stone
- Building limestone is priced by volume
Uses
- Cement, building stone, agriculture
Care
Dissolves in acid. Avoid vinegar and acidic cleaners on prized pieces.
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