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284 SILICATES. 9 h k I m 30-91 29-72 2913 30-31 28-47 48-68 64-72 62-01 46-80 53-34 15-37 16-69 17-58 18-08 17-41 1-19 — lime 0 13 0’31 1-33 1-85 1-28 2-16 0-72 Silica Alumina lied oxide of iron . . Protoxide of manganese Magnesia .... ^ The composition of staurolite from Airolo is represented by am, where a, is li and E&. In staurolite from St. Gotthardt the bases contain about twice as much oxygen as the silica. In the varieties from Bretagne and the Ural the oxygen of the bases is £ of that of the silica. In imbedded crystals in mica slate, talc slate, clay slate, rarely in gneiss, with garnet, kyanite, tourmaline. Is found near Prato on St. Gotthardt, and on the Greiner in the Zillerthal, often attached to crystals of kyanite so that a face of one crystal is in contact with a face of the other, and their edges parallel; at Sebes in Transylvania, near Petersdorf and Goldenstein in Moravia, St. Jago di Compostella in Spain, in the neighbourhood of Oporto, in mica slate and isolated crystals at Quimper and Famine in the department of Finis- terre, Hieres in the department of Var, in some of the Hebrides, in Aberdeenshire, Syra in the Ural, in the mica slate of New England. 157. ANDALUSITE.—Andalusite; Phillips. Andalousite; Hauy. Andalusit; Hausmann, Haidinger. Prismatic. 011,010 = 64° 34'; 101,001=35° 5'; 110,100 = 15° 22'. a 100, b 010, C 001, r 011 > s lOl; rc 35° 26' ha 63° 4i' be 90 0 ba 90 0 sc 35 5 rr > 70 54 ac 90 0 ss' 70 10 ma 46 22 mm! 89 16 FIG. 807. Combinations, cm, sm, cam, csrm, scmb, mcrsJc. Surfaco uneven and rough, seldom smooth, usually covered with films of mica. Cleavage, m more or less distinct; b imperfect; s and a traces. Fracture uneven, splintery, flat conchoidal. Trans parent... translucent on the edges. Lustre vitreous. For a red ray in a plane parallel to c, and polarized in that plane fx = ro2i. The optic axes lie in a plane perpendicular to tho
