MIA'VA, a market-town of North-west Hungary, on the Miava, an affluent of the Morava, 48 m. e.n.e.of Presburg city. There are manufactures of woolen cloth and bag2;ing, and hemp and flax are cultivated. Pop. '69, 9,637.
AirCA, (from the same root with Lat. mieo, to glitter), a mineral consisting essentially of a silicate of alumina, with which are combined small proportions of silicates of potash, soda, lithia, oxide of iron, oxide of manganese, etc., according to which and the some what varying external characters, numerous species have been constituted by mineralo gists COMMON Mica., also called POTASH Mien, contains a notable but variable propor tion of silicate of potash; it contains also a littIe fluorine. It is a widely diffused and plentiful mineral, entering largely into the composition of granite, mica-slate, and some other rocks, veins and-fissures of which it also often fills up. It has a strong, and often almost metallic luster. It is remarkable for the readiness with which it splits into thin elastic plates, which are generally transparent. The thinness and elasticity of these plates readily disting-uish them from those of talc, and of the laminated variety of gyp sum; they are also devoid of the greasy feel of talc. They are sometimes not more than one 300,000th part of an inch in thickness, are generally quite transparent, and are there fore much used in setting objects for the microscope. Plates of Mica of large size are
also used in Siberia, Peru, and 31exico as a substitute for glass in windows. Large plates, often a yard in diameter, are found in these countries, and in Norway and Sweden. Mica is advantageously substituted for glass in lanterns, as it bears sudden changes of temperature better than glass, and in ships:of-war, as it is not liable to be broken on the discharge of cannon. Another use of Mica is for making an artificial avanturine ; is also employed in a powdered state to give a brilliant appearance to walls, and as a sand to sprinkle on writing. In the state of a very fine powder, it is known as Cat's Gold or Cat's Silver, according to its color. It is usually colorless, but sometimes white, gray, green, red, brown, black, and rarely yellow, owing to the presence of iron, manganese, ehroine, fluorine, etc , in its composition. It is sometimes found in beautiful crystals, which are generally rhombic or six-sided tables, Limns, MrcA, or LEPIDOLITE, contains Iithia in small proportion. It is often of a rose color, er a peach-blossom color. It is used for ornamental purposes. It is found in several places in Britain.—MAGNEsrA MicA, or BIOTITE, contains about as much magnesia as alumina. It is often dark green.