374 SILICATES. n 0 P <1 r S 62-97 82-6 61-90 69-00 63-25 61-22 22-29 24-0 22-66 23‘28 2392 23-32 — o-i 0-35 1-18 — 2-40 2’O0 3-0 2-02 6-17 323 8-82 0*54 0-2 o-ii 0-30 0-32 0-36 8’45 8-9 9-43 6-61 0-88 2*56 369 — 3 08 1-75 2-31 trace — (itn 0-39) 1-02 — — — 0-82 — — from the protogyne of Chamouni by Delesse, of liafnefjordite s from Hafnctjord (a = 2-729) by Forchhammer Silica . . Alumina Red ox. iron Lime . . Magnesia . Soda . . . Potash . Loss by ignit. Not decomp. Crystallized and massive, in granite, syenite, gneiss, por phyry, basalt. Is found massive in granite near Stockholm, Ttterby, Troll- hatta, T\edestrand in Norway (avanturine-felspar or sonnen- stein, the play of colours being produced by numerous thin hexagonal plates of hematite), Kimito and other parts of Fin land, Schaitansk in the Ural, Philadelphia in the United States; m attached crystals at Arendal in Norway, in imbedded crys tals in the porphyry of Ajatskaja and Bogoslowsk in the Ural, in the green porphyry of the Muhlenthal near Elbingerode in the Harz, in the porphyry called Verde Antico in the Morea. Hafnefjordite is found in cavities in lava, with augite and umenite, at Hafnefjord in Iceland. 212. LABRADORITE.—Labrador felspar; Phillips. Feld- spath opalin ; Hauy. Polychromatischer Feld-Spath ; Mohs. Labradorit; Hausmann, Haidinger. Anorthic. m 010, p 001, I 110, t 110, y 201. TIG. 389. mp 86° 25' Ip 114 26 pi' 05 34 lm 59 20 Twins. 1. Twin-face m. 2. Twin-face m P■ Massive varieties are sometimes constituted of numerous layers of which each pair is a twin-crystal according to one of e wo laws ahove stated. Cleavage, p very perfect; m rather less perfect; I imperfect. Fracture imperfect conchoidul... uneven, splintery. Faintly translucent. Lustre vitreous in-
