510 IROK. the truncating planes and the neighbouring planes are truncated. 4. Cube truncated on all the edges. 5. Cube truncated on all the edges and angles. The planes of the crystals are smooth, shining, ada mantine, and generally diagonally streaked. Internally it i s glistening, and the lustre is interme- late between vitreous and resinous. The fracture is imperfect foliated, and sometimes un even, or imperfect conchoidal. The fragments are indeterminate angular. It occurs in distinct concretions, which are small gra nular. It is translucent. The streak is straw-yellow. It is soft, inclining to very soft. It is brittle. / Specific gravity, 3.000, Bournon. Chennai Characters, Before the blowpipe it melts, and gives out arsenical vapours. Iron, Constituent Parts. . * 48 Arsenic Acid, 31-0 Arsenic Acid, 18 Oxide of Iron, 4.5 5 Water of crystallisa- 0xide of Co pper, 0.0 o tl0n ’ - 32 silica, - - 4.0 Carbonate of Lime, 2 to 3 Water, - 10.5 100 100 Vauquelin, in Brong. Chenevix, in Pl.il. Min. t. ii. p. 183. Trans . for 1801. GcognosM