WOLFRAM. 551 It yields readily to the knife. It is brittle. It is uncommonly heavy. Specific gravity, 6.885, Elhuyar; 7.130, Gellcrt; 7.1195, Brisson; 5 705, Gmelin; 7.000, Leonard’.; 7.3333, IIany; 7.006, Ktrwan; 6.955, Halchelt; 0.857, UU- niann. ' Chemical Characters. It decrepitates before tl.e blowpipe, but is infusible without addition. It colours glass of borax reddish, when exposed to the exterior flume of the blowpipe. Constituent Paris. Tuiigstic Acid, 64.0 67.00 Oxide of Manganese, 22.0 6.25 Oxide of Iron, Silica, 135 18.10 1.50 99.5 92.75 I)'Elhuyar, Mem. d. l’Acad. Vauyuehn, in Journ. d. Toulouse, ii. ^ %> Geognostic Stlualion. , It occurs in primitive rocks, and generally along with tinstone, and wolfram ; less frequently in veins in grey- wacke, along with galena or lead glance, grey copper-ore, sparry ironstone, and quartz. Geographic Situation. It occurs in gneiss in the island of Rona, one of the M m 4 Hebrides;