Royalty payments to Catamarca Province commenced in April 1998. The Bajo de la Alumbrera deposit is a classic copper-gold porphyry.
Porphyritic dacite intrudes volcanic andesite, chalcopyrite being the main copper mineral.
Near-surface weathered material overlies primary sulphide. The mining area measures 1.8 km by 1.8 km. The latter comprises 100m 3 rougher cells, a regrinding mill, and Jameson Cell cleaner and scavenger flotation. In April 1999, MAA shipped its one-millionth tonne of concentrate. Bajo de la Alumbrera is located at an altitude of 2,500 m in Belen province, some 1,100 km northwest of Buenos Aires.