Volltext Seite (XML)
266 OXIDES, EAETIIS, AXD ACIDS. Lustre vitreous, inclining to resinous. Dark leek-green... blackish-green, greyish-green, blue, black. Streak grey. Brittle. h = 7*6... 8*0. o = 4'23...4‘40. Conducts electricity feebly. Infusible before the blowpipe. Nearly infusible in borax and salt of phosphorus. In powder with soda on charcoal, in the inner flame, deposits a sublimate of oxide of zinc on the char coal In powder fuses with bisulphate of potash into a mass which is completely soluble in water. Is not acted upon by acids or alcalies. ZnAl, part of the Zn being replaced by Mg and Be, and part of the M by ft. Analyses of galinite a from Fahlun, b from North America by Abich, c of a black variety, a = 4 39, from Bodenmais (kreittonite) by v. Kobell:— a b c Alumina 65*14 57*09 49*62 Bed oxide of iron . . . 5*85 9*60 Oxide of zinc . . . . 30*02 34*80 26*67 Protoxide of iron . . . 4*56 7*99 Magnesia 5*25 2*22 3*40 Protoxide of manganese . traces traces 1*44 Silica 3*84 1*22 — According to H. Bose the silica is derived either from a mechanical mixture of quartz, or from the agate mortar in which the mineral was reduced to powder. In imbedded crystals; granular masses; disseminated. Is found in Sweden in Eric Matts mine near Eahlun, in talc slate, associated with blende, galena, gadolinite, and garnet, and at Broddbo near Eahlun; massive at Oester Silfberg near Siither and at Garpenberg with quartz; in Finland at Lojo; Bodenmais ; Haddam in Connecticut, in granite witli beryl, garnet, and cymoplmne. We have observed some single and twin octahedral crystals, apparently gahnite, imbedded in tho interior of a large crystal of garnet from Fahlun. According to Alger, ‘disluite’ is to be considered as a va riety of gahnite. Cubic. 0 ill. 00' = 70° 32'. Yellowish- brown. 11 = 4'5. G = 4*55. Before tho blowpipe dissolves slowly in borax, forming a red glass. Analysis by T. Thomson, as interpreted by Bammelsberg:—alumina 30*49, red oxide of iron 27*96, protoxide of iron 12*55, oxide of zinc 10*80, protoxide of manganese 7*60. Is found with gahnite at Sterling in New J ersey.
