What are pumice rocks?
Pumice forms when lava cools rapidly- so rapid in fact that gas bubbles form which leads to the incredibly porous and lightweight rock.
The way gas gets caught in it is much like how carbonated soda bottles froth when it is shook and then its pressure released, this release of pressure is like the high-pressure gas from a vent, this pressure 'shreds' the magma, turning it into molten froth, as it flies through the air it cools quickly, trapping the gas inside.
Examples of eruptions which produced large swathes of this rock include the Pinatubo Eruption in 1991 and Mount St. Helens.
Uses of pumice:
-In lightweight concrete products/blocks.
-In landscape and horticulture as a decorative feature.
-In cosmetic products, usually scrubbing products for the face, body and practically the feet.