These pumice stones come from the only Canadian volcano, Mount Meager in British Columbia. It is an extremely porous volcanic stone, whose low-density allows it to float. The pumice stone is formed when a temperature of 500 to 600 degrees Celsius is reached. The expulsed lava cools very quickly and the drop in pressure causes outgassing that creates bubbles, which are responsible for the stone's porosity and low density. They are composed of rhyolite, dacite or andesite fragments. Pumice stones have been used since Roman times and are suitable for use on the hands, elbows, soles of feet, and heels.