"Volcanic stone is formed when the lava stream flows and cools down with the air remains and becomes small holes in the final rock. This natural stone has many special features such as sound absorbing and insulation, heat absorbing and preservation, water absorbing and slide proof, Acid & alkali proof, ""Breathing function"" etc.. Now it is so called as “Functional Stone"" which can be used safely in any places for its low radiation, wind erosion proof and durability, sound absorbing and noise lowering, water absorbing and air humidity keeping, dizzy light avoiding, etc. in improving our environment and feelings. www.chinestone.com