OLIGOCLASE. 373 giving^ a striated appearance to the cleavages p. Cleavage. P, perfect; m, less perfect; I, imperfect. Fracture conchoidal • •. uneven, splintery. More or less translucent. Lustre vitre ous, on the more perfect cleavage faces inclining to pearly, on the other faces inclining to waxy. Greenish-white... leek-green, greenish-grey, reddish-grey, flesh-red. Streak white. H = 6'0. G = 2'63...2 74. Melts before the blowpipe much more easily than felspar and albite into a white porous glass. Is not decomposed by acids. Na 2 Si 3 + 2AlSi 3 , a considerable part of the soda being re placed by lime, potash and magnesia. Analyses of oligoclase a from Danvikszoll near Stockholm, o from Ttterby, both by Berzelius, c from Arendal by Hagen, “ from Ajatskaja to the north of Katharinenburg by Francis, ® from Arendal by Eosales, f from Schaitansk in the Ural by Bodemann :— Silica Alumina . . lied oxide of iron Lime Magnesia . . . Soda Potash , . . . a I) 0 d e / 63-70 01-56 63-51 61-06 62-70 64-25 23-95 23 80 23-09 19-08 23-80 22-24 O'oO — — 4'11 0-62 0-64 2-06 3-18 2'44 2'16 4'60 2-57 0'65 0’80 0-77 1-05 0-02 1'14 8-11 9-67 9-37 7'55 8-00 7-98 1-20 0-38 219 3-91 1-05 1'06 Analyses of oligoclase g from Warmbrunn in Silesia by Itam- Ulelsberg, h from Kimito in Finland (a = 2‘63) by Chodnew, t from a boulder at Flensburg (o = 2'65l) by Wolff, k from Tvedestrnnd in Norway, I from the gneiss of the deep Fiirsten- stolle near Freiberg (o = 2-03...2-66), m from Marienbad in Bohemia (a = 2-631), both by Kersten:— Silica . , ■Alumina . Bed ox. iron Lime Magnesia . Soda Potash .' .’ 3 h i h I m 63-94 63-80 64-30 01-30 62-97 63-20 23-71 21-31 22-34 23 77 23-48 23-50 traces — — 0'36 0-51 0-31 2-62 0-47 4-12 4-78 283 2-42 traces — — — 0-24 0-25 7'66 12-04 O'Ol 8’50 7-24 7-42 2-17 1-98 — 1'29 2-42 2-22 Analyses of oligoclase n from the volcanic rocks of Teneriffe (o = 2-68...2-60) by Deville, o from Arriege by Laurent, p from Boden near Marienberg (a = 2'60...2'68) by Kemdt, q from Mellandamsbackcn near Saida (a = 2'69) by Svanbcrg, r