pumicite
/ˈpʌmɪsaɪt/
noun
- A light, porous volcanic rock used as an abrasive or in construction.
- The ancient Romans used pumicite in their concrete to make it lighter.
- The gardener used pumicite to smooth the rough edges of the stone pathway.
- Pumicite is often added to soil to improve drainage in potted plants.
Synonyms