42 ruby Family. External Characters. Its colour is greenish-white, of various degrees of in tensity, which passes into light .greenish-grey, and even into mountain-green, asparagus-green, Berlin-blue, and azure-blue; it is sometimes also pearl-grey, which passes into flesh-red, cochineal-red, crimson-red, and hair- brown. When cut in a semicircular form, it often presents an opalescent star of six rays. It occurs massive, disseminated, in rolled pieces, and crystallised. Its principal crystallizations are the follow ing : 1. Equiangular six-sided prism. 2. Same prism, having its alternate angles truncated. 3. Same prism, having its terminal edges and alternate angles truncated. 4. When the truncations on the angles of N° 2. in crease very much in magnitude, there is formed a three- planed acumination, in which the acuminating planes are set on the alternate lateral edges of the prism. 5. When the truncations on the edges increase very much, a six-planed acumination is formed; and when the prism becomes very short, or disappears, there is formed a simple six-sided pyramid; and if the prism is acumina ted on both extremities, a double six-sided pyramid; and in both cases the summits of the pyramids are trun-i fcated. The crystals are middle sized. Externally, they are dull and rough. The lustre of the principal and cross fracture is shining and glistening, and is either vitreous inclining to resi nous, or pearly inclining to adamantine. Thr
