Pumice or pumice ( /ˈpʌmɪs/), called pumicite in powder or dust form, is a volcanic rock consisting of coarse-textured volcanic glass that is highly vesicular and contains crystals. On light color. Scoria is another vesicular volcanic rock which differs from pumice in having larger vesicles, thicker vesicle walls and is darker in color and denser.
Pumice is formed when very hot, high-pressure rock is ejected energetically from a volcano. The unusual foaming configuration of pumice occurs due to its simultaneous rapid cooling and rapid depressurization. Depressurization creates bubbles by decreasing the solubility of gases (including water and CO2) that dissolve in the lava, causing the gases to dissolve quickly (such as the CO2 bubbles that appear when a carbonated drink is opened). Simultaneous cooling and depressurization freezes the bubbles in the matrix.
Pumice consists of highly microvesicular pyroclastic glass particles with very thin and translucent bubble walls of extrusive igneous rock. Pumice is a common product of explosive eruptions (plinian and ignimbrite formation) and generally forms a zone at the top of silica lava. Pumice has a porosity of 64-85% by volume and floats on water.