250 GYPSUM FAMILY. grey, so that it often passes into a kind of smoke-grey; sometimes the colour is intermediate between Berlin and smalt blue; and rarely, and then only in spots, it is brick-red and aurora-red. It occurs massive. Some parts of the fracture-surface (the radiated) are splendent and pearly, others (the splintery) are glistening. The fracture is partly short, narrow, straight and stel lular radiated, and partly splintery. The fragments are indeterminate angular, and rather blunt-edged. It is translucent. It is semi-hard. Specific gravity, 2.940, Klaproth. 2.900,3.000, Hau* mann. I Constituent Parts. Lime, - - . 4 2 . 0 0 Sulphuric Acid, - - 57.00 Oxide of Iron, - . ojo Silica, - . . o.25 99.35 Klaproth, Beit. b. iv. s. 229. Geognostic and Geographic Situations. Along with sparry anhydrite and compact gypsum, it forms a bed in granular gypsum, at the village of Tiede, near Brunswick; and is also found at Ilall in the Tyrol, Sulz on the Neckar, Carinthia, and Ischel in Austria. Uses. The blue varieties are sometimes cut and polished for ornamental purposes; but it is said that it does not form so good a stucco as common gypsum. Fourth