322 SILICATES. In attached crystals, reniform, and compact. Is found at Moresnet near Liege, Stolberg near Aix-la-Chn- pelle, Eaibel in Carinthia, Kucsaina in Servia, Franklin in New Jersey. The figure of troostite (combination rsab), which till lately was supposed to consist principally of silicate of protoxide of manganese,^ is given on Breithaupt’s authority. His observa tions make rr = 60° nearly. ^ 182. G-ADOLINITE.—Gadolinite; Phillips, Hauy. Hemi- prismatisches Melan-Erz; Mohs. Gadolinit; Hausmann, Haidinger. Prismatic. 011,010=25° 4o'; 101,001=50° 30'; 110,100=59° 45'. b 010, c 001, e 104, m 110, r ill. r is hemihedral with parallel faces. tig. 330. be 0 0 05 0' ee 16 52 mb 30 15 mm! 60 30 TC 67 27 rm 22 33 Cleavage none perceptible. Fracture conchoidal...uneven. Translucent on the edges...opaque. Lustre vitreous, inclining to resinous. Black, seldom red. The black varieties greenish by transmitted light. Streak greenish-grey. n = 8’5. g = 4’2 ...4'4. Sometimes magnetic. Infusible, or fusible with difficulty before the blowpipe. Some varieties from Hitteroe glow brightly when heated, and their specific gravity is increased by ignition from 4’36 to 4'03 ; others merely intumesce. Soluble readily in borax, and par tially in salt of phosphorus, forming a glass coloured by iron. Completely decomposed by hydrochloric acid leaving a jelly of silica. After ignition is decomposed with difficulty. Silica .... Yttria . . Oxide of cerium Ox. lanthanium Protoxide of iron Glucine . . . 1 Ytterby c, d, Berlin: a b C d e / 25-78 25-59 24-65 24-65 24-86 24-86 45-67 44 06 49-60 51-38 48-32 51-40 1-81 — 1 5‘24 4-75 6 33 J 7-64 7-00 7-41 11-68 12-13 1603 14-69 14-80 13-01 9-67 10-18 213 traces 8’60 4-80