pumice
Definitions
A very light, porous volcanic rock formed when a gas-rich froth of glassy lava solidifies rapidly.
A substance made from this rock, used in powdered or block form for smoothing, polishing, or scrubbing.
Examples
The gardener used a piece of pumice to scrub the stubborn dirt off his hands.
Pumice is a lightweight volcanic rock that is often used in beauty products to exfoliate the skin.