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286 SILICATES. Analysis of chiastolite a from Lancaster by Bunsen, h by Jackson:—• Silica 39-09 33‘0 Alumina 58 - 66 6ro Oxide of manganese . . o - 53 j* 4-o Lime 0 -2i — Volatile matter .... 0-99 h 1-5 Chiastolite occurs imbedded in clay slate near Bareges, in the valleys of Luchon and Gistain in the Pyrenees, Serra de Marao in Portugal, St. Jago di Compostella, near Santa Elena m the Sierra Morena in Spain, St. Brieux in Bas Bretagne, Gefrees m the Fiehtelgebirge, Greifenhagen in the Harz, the Wolfscrag near Keswick in Cumberland, Agnavanagh in Wick low, m dolomite on the Simplon, in grey limestone at Coule- doux in La Haute Garonne, at Sterling and Lancaster in Mas sachusetts, Siberia, Mexico. 158. KYANITE.—Kyanite ; Phillips. Disthene; Hauy. Prismatischer Disthen-Spath; Mohs. Disthen ; Hausmann. Kyanit; Haidinger. Anorthic. em 0 0 <N 45' im 34 19 tm 73 44 km 48 37 pm 79 10 pt 88 45 FIG. 309. Combinations, putt..k.i.e. The faces m, t are sometimes striated parallel to their intersections with each other. Twins. 1. Twin-face m. 2. Twin-axis the axis of the zone mt. Pairs of crystals occur also united by the faces m, so that the faces p of the two individuals, and the axes of the zones mt are parallel, the faces t forming a re-entering angle. Cleavage. m very perfect, t less perfect, p least perfect. Fracture uneven. Transparent.. .translucent. Lustre, pearly on m, vitreous on the other faces. Colourless, white, passing into blue, green, and sometimes grey. Stripes of blue occur frequently on a lighter ground. On looking through a blue crystal in a direc tion parallel to the edge mp, it is of a deep blue colour when the light is polarized in a plane perpendicular to m, and colour less when the light is polarized in a plane parallel to m. In a direction nearly perpendicular to m, the colour is lighter or darker according as the light is polarized in planes parallel or perpendicular to the edge mi. Streak white. Brittle, it = 6'0
