Rocksday

Pumice

Volcanic glass so full of gas bubbles that it floats on water. It forms in explosive, gas-rich eruptions.

Pumice specimen
Photo: User MPF on en.wikipedia, CC BY-SA 3.0, via Wikimedia Commons

How to identify pumice

  • Very light — it floats.
  • Pale gray or white.
  • Full of tiny bubbles and stretched fibers.
  • Feels rough and scratchy.

Often confused with

Where it's found

  • Lipari, Italy
  • Santorini, Greece
  • Mount St. Helens, Washington
  • Taupō, New Zealand

Uses

Pumice stones, stonewashed jeans and lightweight concrete.

Rock tumbling

Not suitable for tumbling.

Did you know?

After a 2021 eruption near Japan, floating pumice rafts drifted for months and clogged harbors.

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