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Show Pumice Stone. Pumice stone is a porous feldspathic scoria from volcanoes. The pores are linear and so fine as often to be barely visible except by means of a magnifying glass. Its specific gravity is 2.2 to 2.4 water being the unit but by reason of its spongy texture pieces are often buoyant enough to float on water. It consists chiefly of silica, with sometimes some-times 17 per cent of lumina, 6 per cent of oda and 4 per cent of potash. It is of grayish shades of color, passing into yellow and brown. The chief source from -which it is obtained for commercial commer-cial pnrposes is Canipo Bianco, one of the Lipari islands, where it forms a hill 1 nearly 1,000 feet high. In the arts pumice is largely employed, mostly in a pulverized state, as a polishing material mate-rial for ivory, wood, glass, marbles, etc. It is also used in lump for grinding and smoothing metallic surfaces, leather, etc., and in the preparation of parchments, parch-ments, etc. Quantities of. the pulverized pulver-ized pumice are used in making fancy soaps. Brooklyn Eagle. |