Pumice
From Conservapedia
Pumice is a light-colored, frothy volcanic rock, usually of dacite or rhyolite composition, formed by the expansion of gas in erupting lava. Commonly perceived as lumps or fragments of pea size and larger but can also occur abundantly as ash-size particles.[1]
Because of its numerous gas pockets, pumice commonly floats on water.[1]
Pumice stones are used domestically as a mild abrasive to remove hard skin.
