What's That Rock?Basalt
A dark, fine-grained volcanic rock that forms from cooled lava. It makes up most ocean floors.
How to identify Basalt
- Dark and fine-grained, grains too small to see
- May have small round holes (vesicles) from gas bubbles
- Heavier than granite
Often confused with
Is Basalt valuable?
Common.
What changes the price
- Common rock: almost no collector value as a specimen
- Columns, vesicular or unusual pieces may sell as décor, but remain inexpensive
- Landscape and building stone is priced by the ton
Uses
- Road gravel, building stone, rock wool insulation
Care
Safe to wash.
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