What's the noun for pumicates? Here's the word you're looking for.
pumice
A light, porous type of pyroclasticigneous rock, formed during explosive volcanic eruptions when liquid lava is ejected into the air as a froth containing masses of gas bubbles. As the lava solidifies, the bubbles are frozen into the rock.
“There are presently twenty-two developed pits used for the extraction of aggregate ' clay, and pumicite.”
“Pumice is in thin beds or as blocks, with extensive deposits of pale grey pumice and pumicite on the plains east of Dhamar, already mined from pits using front-end loaders.”
