Pumice Powder, Super Fine Pumice (1oz) is a volcanic ash which is formed when lava is permeated with gas bubbles during the solidification process. Because lava has similar properties and chemical make-up as glass, pumice is very abrasive but unlike glass, it is very soft. Pumice is the softest abrasive media in use today. All Natural. Use a little sugar scrubs and see how wonderful it works; gentle enough to be used on the face and all skin types, even sensitive skin.