294 SILICATES. Cleavage, m, distinct, but interrupted; a, perfect; b, imperfect. Fracture uneven. Opaque, in some varieties translucent on the edges. Lustre pearly on the planes of most perfect cleavage; on the other faces vitreous ; on surfaces of fracture inclining to resinous. Greyish-black, greenish-black ; in many varieties almost copper-red on the planes of perfect cleavage. Streak greenish-grey. Very tough, h = 6’0. & = 3 39. Before the blowpipe melts more or less readily into a greenish-black glass which is frequently magnetic. Readily soluble in borax, forming a greenish glass. Is not acted upon by acids. RSi, where R is principally magnesia and protoxide of iron, usually with small quantities of lime and protoxide of manga nese. Analyses of hypersthene a from the island of St. Paul, b from the island of Skye, both by Muir, o from Labrador by Damour:— a b C Silica . . .... . 46'11 51-35 51-38 Alumina 4-07 0’37 Magnesia . 25-87 11-09 2131 Lime 5-38 1-84 309 Protoxide of iron . . . . 12-70 3392 21-27 Protoxide of manganese. 5-29 — 132 "Water 0-48 0-50 — In crystals and crystalline, granular masses. Is found in the island of St. Paul on the Labrador coast in rolled masses and as a constituent of a greenstone rock, Green land, in many parts of Norway in hypersthene rock, in the island of Skye, Penig in Saxony, Ronsbcrg in Bohemia, Mon- zoni in the Tyrol, Elfdalen in Sweden, Neurode in Silesia, and in boulders in the neighbourhood of Berlin. 163. BRONZITE.—Bronzite; Phillips. Diallago (in part) ; Hauy. Hemiprismatischer Schiller-Spath ; Mohs. Bronzit; Hausmann, Haidinger. Oblique. Isomorphous with augite. a ioo, b oio, c ooi, m no, all cleavages. mb 43° 0' ab 90 0 mb 47 0 mm' 86 0