Pumice is an igneous rock that can be made up of various minerals such as feldspar, hornblende, augite and zircon. It is a light-colored rock that forms during a volcanic eruption.
Pumice is a mineraloid, an amorphous volcanic glass. Most pumice stones have a rhyolitic composition, though they can have a basaltic or andestic composition.
The vesicles or pores in pumice are created by gas bubbles that were trapped during the rapid cooling of frothy magma. Pumice has a low specific gravity giving it the ability to float on water. It is used in concrete blocks, to make them lighter, and in creating stone-washed denim, pencil erasers, and cat litter.