Talc, a species of fossil, found in England, Bohemia, Spain, etc. comprehending 3 varieties, namely:
3. The Schistose Talc is of a slaty nature, and a grey hue, spotted with white, green, or blue; but, on exposure to the air, it becomes white and scaly.
This mineral is employed in preparing compositions for earthen vessels : on account of its smoothness, brightness, and unctuous quality, it has been celebrated as a cosmetic; and various unsuccessful experiments have been made, with a view to extract from it oils, salts, and other supposed ingredients. - When combined, with alkaline salts, it is fusible in a strong heat, and forms a transparent, handsome, greenish-yellow glass. if equal portions of talc and of chalk be melted together with one-fourth part of borax, the mixture will produce a fine pellucid greenish glass, which is of considerable lustre and hardness: gypsous earths may also with advantage be substituted for the chalk, and the result will be a beautiful, pellucid yellow glass, of equal brightness and durability. - Talc is subject, on im-portation, to a duty of 2 1/2d. per lb.