Thrown out of an active volcano during an eruption, pumice is lava that is so full of gas bubble holes that pumice is very light and can sometime float. I remember my mother in Liverpool, England, in the 1950's using a pumice stone to wash, clean and whiten the front door step of the small terraced house we lived in at that time. Pumice stone is still used today, especially by women who used the pumice stone to sand away the hard skin on their heels.