pumice

hangata hohkakivellä

hohkakivi A light, porous type of pyroclastic igneous 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.
1912, w:Katherine Mansfield|Katherine Mansfield, The Woman at the Store, Oxford World's Classics 2002, page 10

The wind blew close to the ground - it rooted among the tussock grass - slithered along the road, so that the white pumice dust swirled in our faces - settled and sifted over us and was like a dry-skin itching for growth on our bodies.