CREDNEEITE. 235 The faces a, m, b are striated parallel to their intersections with each other. Cleavage, a. Opaque. Lustre metallic, feeble. Light steel-grey. Streak grey, h = 6'5... 7'0. a = 4'838...4'880. Chemical characters the same as those of pyro- lusite. Mn, manganese 63'27, oxygen 3673. Analysis of polianite from the Maria Theresia mine near Flatten by Plattner:— Red oxide of manganese itnMn . . . 87'27 Oxygen 12‘11 Red oxide of iron and alumina . . . 077 Water °' 32 Silica O' 13 Is found in the Procopzccho and the Maria Theresia mine near Plattcn in Bohemia, the Adam Heber mine at Schneeberg, Tannenbaum Stolln near Johann-Georgcnstadt, Spitzleute near Schneeberg, Hirsch near Geyer in Saxony, the Eiserne Hardt in Siegen. According to Haidinger, polianite is pseudomorphous braunite in the form of pyrolusite. 122. CREDNERITE.—Mangankupferoxyd ; Hausmann. Oblique. Cleavage very perfect parallel to the end faces of an oblique prism; less perfect parallel to the lateral faces. Fracture uneven. Opaque. Lustre metallic on the principal cleavages, less bright on the other cleavages. Iron-black. Streak black, inclining to brown, n = 4'5...6'0. G = 4'89...5'07. In the matrass exfoliates and loses its lustre. Before the blowpipe with soda on charcoal yields a malleable bead of popper. With borax in the outer flame forms a violet glass ; in the inner flame a green glass, which at last becomes red and °paque. In nitric acid the oxide of copper is dissolved, leaving a black residue. Is readily soluble in hydrochloric acid with evolution of chlorine, forming a green solution. Analysis by Credner:— Oxide of copper Oxide of manganese iin Mn . . 56 73 Is found in cleavablo granular masses with pyrolusite and bausmannitc at Eriedrichrodc in Thuringia. Cvednerite is liable to decomposition, in consequence of which the cleavages become more distinct, the colour changes a blackish-blue, n is reduced to 2'6, and G to 471.