pumice

They have all been at work like her, spouting ashes and pumice and rocks and lava.

And from that cloud showered these hot, pelting pebbles of pumice stone.

You know what this is in the case of a sponge, or pumice stone.

The world's principal source for pumice is the Lipari Islands, Italy.

Pumice stone might do it, but it would take your skin off, too.

Here, Oliver, lad, look at the great pieces of scoria and pumice.

But of pumice in connection with the pitchstones of Eigg, more anon.

Ashes and pumice heated to incandescence were blown through the air.

The islands are all volcanic, all ash and cinders, lava and pumice.

Neither the pumice stone nor the dust, then, could have set wood on fire.