3. Alteration stage of phyrrhotite: fundamentally characterized by the alteration of phyrrhotite, from which results mainly siderite and marcasite, due to the iron released in the alteration process. Added to this iron is the iron released in the dissolution of the pyrite-I giving rise to a second generation of pyrite, magnetite and hematite. In this phase, alteration of stannite due to reaction with the siderite, forming covellite, chalcopyrite and cassiterite also occurs. It is also at this stage that the silver salts usually associated with bismuthinite and accompanied by sphalerite and / or chalcopyrite are deposited.