pumice

Everyday

1. Pumice is a very light, rough grey rock full of tiny holes, made when frothy lava from a volcano cools quickly; it can float on water. tree →
2. A pumice stone is a piece of this rock used to rub away hard skin, for example on your feet. tree →

In the lessons

In science lessons on rocks, pumice is an igneous rock formed from volcanic lava; because it is full of gas bubbles, it floats — a surprising fact for a rock. After some eruptions, rafts of floating pumice drift on the sea. In everyday life, pumice stones are in bathrooms. Common phrases: «pumice stone», «a raft of pumice», «floating pumice».

Examples

• Pumice is the only rock that floats on water. tree →
• Pumice forms when bubbly lava cools very quickly. tree →
• Nan uses a pumice stone on her heels. tree →
• After the eruption, a raft of pumice floated across the Pacific. tree →
• We tested rocks in water, and the pumice floated. tree →
• Pumice is rough, light and full of holes. tree →
• Some toothpastes and cleaners contain powdered pumice. tree →

Note

Uncountable as a material; «a pumice stone» for one piece. Say PUM-iss. Strictly, not every pumice floats for ever — it sinks when its holes fill with water.