pumice

The Paiute-Shoshone Indians later chipped away at the red pumice stone, which exposed the lighter rock minerals underneath, according to the Bureau of Land Management.

Besides the acids and bacteria, the balls also contained volcanic rock pumice.

They had also visited Pompeii, the ancient Italian city buried under volcanic ash and pumice when Mt.

A wide residential and commercial block, known as "Region 9", is being cleared of several metres of overlying pumice and ash thrown out by Vesuvius almost 2,000 years ago.

In addition to lava, volcanos eject large amounts of pumice, ashes and gases as a fast-moving flow, known as "pyroclastic flow," and its sediments are a valuable data source on past eruptions.