copper-nickel. 519 The uneven has the least, the conchoidal the greatest de gree of lustre. The fragments are indeterminate angular and sharp- edged. , . , It is usually compact, sometimes also m coarse and - small granular distinct concretions. It is semihard in a high degree; it yields with difficul ty to the knife. It is rather brittle It is rather difficultly frangible. It is uncommonly heavy. ^ . nDr r r . a , „ . Specific gravity, 7.560, Gcllert; G.608G-6.6481, Bru. son. Chemical Characters. Before the blow,,ipe it gives out an arsenical vapour, and then fuses, though not very readdy, into a daik sco ria, mixed with metallic grains ; is soluble u, mtro-muri- atic acid, forming a dark-green liquor, from which caus- tic alkali throws down a pale-green prec.pilate, whereas from a solution of copper the precipitate is dark-brown. Constituent Parts. It is a compound of Nickel and Arsenic. Gcognostic Situation. It generally occurs in primitive rocks, such as gneiss, mica slate, syenite and clay-slate, along with tin-wlnte eohalt-ore, and silver white cobalt-ore; also in transdon rocks and floetz rocks, particularly the first fleets lime stone, and the limestone which occurs in one of the for mations of black coal. The minerals with which it is K k 4 most