Formula. Cu. Behavior (1) in glass-bulb. -- (2) in open tube. -- (3) on charcoal. Fuses to a brilliant metallic bead, which on cooling becomes covered with a coating of black oxide. (4) in forceps. Fuses and colors the outer flame blue. (5) in borax. In the oxidizing flame dissolves and then gives the copper reactions. (6) in mic. salt. As in borax. (7) with carb. soda. -- (8) Special reactions. -- * * * * * Mineral. Vitreous Copper Formula. Cu^{2}S. Behavior (1) in glass-bulb. -- (2) in open tube. Evolves SO^{2} and, when pulverized and gently heated for some time is converted into CuO. (3) on charcoal. Fuses to a bead, which spirts considerably and gives off SO^{2}. When pulverized and gently roasted, is converted into CuO. (4) in forceps. -- (5) in borax. The roasted mineral gives the copper reaction, and sometimes also a slight iron-reaction. (6) in mic. salt. As in borax. (7) with carb. soda. In the reducing flame is decomposed, forming NaS and metallic copper. If the former be cut out and laid upon silver, it gives the sulfur reaction. (8) Special reactions. -- * * * * * Mineral. Copper pyrites Formula. [,Cu=][,,,Fe=]. Behavior (1) in glass-bulb. Decrepitates, sometimes gives a sublimate of sulphur and becomes bronze colored on the surface. (2) in open tube. Evolves SO^{2} and is finally converted into a dark red mixture of Fe^{2}O^{3} and CuO. (3) on charcoal. Fuses readily with much ebullition and is magnetic on cooling. (4) in forceps. -- (5) in borax. As the preceding; but when the copper has been removed by reducing on charcoal, the bead shows a strong iron color. (6) in mic. salt. As the preceding, but the color in the oxidizing flame is green, owing to the presence of iron. (7) with carb. soda. Yields a bead of metallic copper and some magnetic oxide of iron which remains on the charcoal. The fused gives a sulphur reaction on silver. (8) Special reactions. -- * * * * * Mineral. Fahlerz Formula. ([,Cu=][,Ag][,Fe][,Zn])^{4} ([,,,Sb][,,,As]). Behavior