_The colour of mica is greenish, sometimes nearly black, reddish, brown, yellow, or silvery white, with, occasionally, a metallic lustre on the surface. Mica is so soft as easily to be scratched; and, when divided across the plates, seems rather to tear than break._ This is one of the most abundant mineral substances that is known. It not only occurs in a massive and crystallized state, but it enters into the composition of many rocks; is found filling up their fissures, or crystallized in the cavities of the veins which traverse them. In some countries, as in Siberia, it is an article of commerce, and is obtained from mines like other minerals. From these it is extracted by hammers and chisels. It is then washed, to free it from the impurities which adhere to it; split into thin leaves or pieces; and assorted into different kinds, according to their goodness, purity, and size. We are informed by the Abbé Haüy, that plates of mica a yard or more in width have been obtained from the mines in some parts of Russia. Thin plates of mica are adopted, in many parts of Siberia and Muscovy, to supply the place of glass for windows. In the shipping of Russia it is considered preferable to glass, as the concussion produced by the firing of the guns does not shatter it. It is employed instead of window glass in Peru and New Spain; and also in Pennsylvania. Mica may be advantageously substituted for horn in lanterns, as it is not only more transparent, but is not susceptible of injury from the flame of the candle. It has, however, the inconvenience of soon becoming dirty; and of having its transparency destroyed by long exposure to the air. Mica is used for enclosing objects that are intended to be viewed by microscopes. So plentiful is this substance in Bengal, that, for the value of five shillings, as much of it may be purchased as will yield a dozen panes, each measuring about twelve inches in length and nine in breadth, and so clear as to allow of ordinary objects being seen through them at the distance of twenty or thirty yards. Mica, when powdered, is sold by stationers on the Continent, in place of sand, for absorbing ink in writing, but it does not dry sufficiently quick to be of much use in this respect. In Russia it is employed in different kinds of inlaid work. It is sometimes powdered, and intermixed with the glaze in particular kinds of earthen ware. The heat which melts the glaze has no effect on the mica: hence it appears, dispersed throughout the glaze, like plates or scales of silver or gold. Some artists use it in making artificial avanturines (85). It must be observed that the best mica is of a pure pearl colour; and, when split into leaves, presents a smooth surface. SOAPSTONE FAMILY. 124. _STEATITE, or SOAPSTONE, is a soft and unctuous substance, which has much the appearance of soap; and is generally of a white or grey colour, intermixed with greenish or yellowish shades._