MONTICELLITE. 315 he appearance of belonging to the anorthic system, in conse quence of the enlargement of some faces at the expense of others. According to Breithaupt the crystals are pseudo- morphous. The pyrorthite from Kararfvet near Fahlun is supposed to be allanite containing a mechanical admixture of carbon. When ignited at one point it bums on without flame or smoke; after winch it becomes white, very porous, and may be melted with difficulty into a black globule. With borax in the inner flame torms a blood-red glass which becomes yellow on cooling. According to Berzelius, it consists of: — Silica Alumina .... Lime Protoxide of cerium . Protoxide of iron Yttria Protoxide of manganese Water Carbon and loss . . 10-43 369 1'81 13-92 6-08 4-87 1'39 26-60 31.41 176. MONTICELLITE.— Monticellite ; Brooke. Philo sophical Magazine, October, 1831. Monticellit ; Mohs, llausmann, Haidinger. Prismatic. 011,010 = 37° 22'; 101,001:= 48° 46'; 110,100 = 48° 65'. a loo, k 101, s 110, n 120, e 122. FIG. 327. ha 41° 14' ea O o 64' kk' 97 32 en 35 0 sn 48 65 ee 38 12 na 68 27 ee" 97 20 nri 47 6 e'e" 110 0 No cleavage observable. Nearly transparent. Lustre vitreous. Colourless, yellowish, ii = 6-6. g = 3-245...3'275. In powder soluble in hydrochloric acid. C 2 Si + Mg 2 Si, Scacchi. Is found in crystals imbedded in granular limestone, with nbca and augite, on Monte Somma. The angles between the faces of monticellite cannot be de termined with much accuracy, on account of the want of even ness of the faces. They approximate to those of olivine, yet p 2
