Volcanic stone (volcanic rock or pumice) is a dense porous vitreous lava formed by the rapid expansion of internal gases after the
sudden cooling of magma in the process of volcanic eruption. The pore volume accounts for more than 50% of the rock volume.
Because of the porosity, light weight, can float on the water is called pumice. It is characterized by high strength, heat
preservation, heat insulation, sound absorption, fire prevention, acid and alkali resistance, corrosion resistance, and no
pollution, no radioactive etc..
