Definify.com
Webster 1913 Edition
Pumice
Pum′ice
,Noun.
(Min.)
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
. Webster 1828 Edition
Pumice
PUM'ICE
,Noun.
A substance frequently ejected from volcanoes, of various colors, gray, white, reddish brown or black; hard, rough and porous; specifically lighter than water, and resembling the slag produced in an iron furnace. It consists of parallel fibers, and is supposed to be asbestos decomposed by the action of fire.
Pumice is of three kinds, glassy, common, and porphyritic.