18 HORNBLENDE FAMILY. It occurs massive; and crystallised in the following figures: Very oblique rhomboidal four-sided prism, in which either the acute or the obtuse edges are truncat ed, or both are truncated in the same crystal. Some crystals appear to be truncated on the ter minal edges and angles *. The crystals are middle-sized, also small, and very small; seldom single, generally many resting on one an other, or they are scopiformly aggregated. T. he external and internal lustre is vitreous, slightly inclining to pearly. The fracture is narrow and straight radiated, some times passing into fibrous, generally scopiformly diver ging, seldom parallel, and principally in the varieties in which the fracture inclines to fibrous. The fragments are splintery and wedge-shaped. It occurs in thick prismatic concretions, which inclose smaller ones of the same kind. It is translucent. It is brittle. It is uncommonly easily frangible. It is traversed by rents. It is semi-hard : it scratches glass, but is scratched by quartz. Specific gravity, 3.175, Karsten. 3.4050, Hausmann. Chemical * According to Count de Bournon, the primitive form of actynolitc dif fers from that of hornblende, although they arc said by Hauy to be identi cal. He says the primitive crystal of aclynolite is a rhomboidal tetrahedral prism, of about 130° and SO 0 , in which the terminal planes are inclined to the axis, so as to form with the edges 50° of the prism angles of 91° and 85°,—Vid. Bournon’s Catalogue Min, p. 86.
