A very light porous volcanic scoria, usually of a gray color, the pores of which are capillary and parallel, giving it a fibrous structure. It is supposed to be produced by the disengagement of watery vapor without liquid or plastic lava. It is much used, esp. in the form of powder, for smoothing and polishing. Called also pumice stone.
- A light, porous, glassy lava, used in solid form as an abrasive and in powdered form as a polish and an abrasive.
- To clean, polish, or smooth with pumice.