NATIVE ARSENIC. 525 Externally it is either rough or granulated, and very feebly glimmering. Internally, on the fresh fracture, it is usually glisten* ing, incliniug to glimmering, sometimes shining, and the lustre is metallic. The fracture is small and fine-grained uneven, some times imperfect, and curved foliated; rarely narrow, straight, and seopiform radiated. The fragments are indeterminate angular, and rather sharp-edged. It occurs in thin, curved lamellar distinct concretions, and seldom in small and fine granular concretions. It is semihard in a high degree. It is very difficultly frangible. It is sectile. The streak is shining and metallic. When struck, it has a ringing sound, and emits an ar senical odour. Specific gravity, 5.7249-5.7033, Brisson ; 5.070, Air- Wail. ' r Chemical Characters. Before the blowpipe it yields a white smoke, diffuses ®n arsenical odour, burns with a blue flame, is gtaduaily and almost entirely volatilised, and deposites a white coating on the coal. O Constituent Parts: u ! It usually contains a small portion of iron, and when it occurs with gold or silver ores, a little gold or silver. Geognostic