Rottenstone

Rottenstone, a soft and earthy stone, consisting chiefly of alumina, with about 10 per cent. of carbonaceous matter and a little silica. It is sup- posed to be formed by decomposition of shale or siliceous limestone. It is found in Derbyshire, England, in Wales, and near Albany, in the state of New York. It is brown—either grayish, reddish, or blackish. It is soft and easily scraped to powder, and is well known to housewives, being much used for cleaning and polishing brass and other metals.