The Toquepala porphyry copper deposit is located on the western slopes of Cordillera Occidental, in the southern-most Andes Mountains of Peru. The deposit is part of a mineral district that contains two additional known deposits, Cuajone and Quellaveco.

The Toquepala deposit is in the southern region of Peru, located on the western slope of the Andes mountain range, approximately 120 kilometers from the border with Chile. This region extends into Chile and is home to many of the world’s most significant known copper deposits. The deposit is in a territory with intrusive and eruptive activities of rhyolitic and andesitic rocks which are 70 million years old (Cretaceous-Tertiary) and which created a series of volcanic lava. The lava is composed of rhyolites, andesites and volcanic agglomerates with a western dip and at an altitude of 1,500 meters. These series are known as the Toquepala Group. Subsequently, different intrusive activities occurred which broke and smelted the rocks of the Toquepala Group. These intrusive activities resulted in diorites, granodiorites and dikes of porphyric dacite. Toquepala has a simple mineralogy with regular copper grade distribution. Economic ore is found as disseminated sulfurs throughout the deposit as veinlets, replenishing empty places or as small aggregates. Ore minerals include chalcopyrite (CuFeS2), chalcosine (Cu2S) and molybdenite (MoS2). A secondary enrichment zone is also found with thicknesses between 0 and 150 meters.

Toquepala operations consist of an open-pit copper mine and a concentrator. The mine is located in southern Peru, 30 kilometers from Cuajone and 870 kilometers from Lima, at an altitude of 3,220 meters above sea level.

Our Toquepala operations utilize a conventional open-pit minning method to collect copper ore for further processing in our concentrator.

Material with a copper grade over 0.40% is loaded onto rail cars and sent to the crushing circuit, where rotating crushers reduce the size of the rocks by approximately 85%, to less than one-half of an inch. The ore is then sent to the rod and ball mills, which grind it in a mix with water to the consistency of fine powder. The finely ground powder mixed with water is then transported to flotation cells. Air is pumped into the cells producing a froth, which carries the copper mineral to the surface but not the waste rock, or tailings. The bulk concentrate with sufficient molybdenum content is processed to recover molybdenum by inverse flotation.

Tailings are sent to thickeners where water is recovered. The remaining tailings are sent to the Quebrada Honda dam, our principal tailings storage facility.

The SX-EW facility at Toquepala produces grade A LME electrowon copper cathodes of 99.999% purity from solutions obtained by leaching low-grade ore stored at the Toquepala and Cuajone mines. The leach plant commenced operations in 1995 with a design capacity of 35,629 tons per year of copper cathodes. In 1999, the capacity was expanded to 56,000 tons per year.

Copper oxides from Cuajone with a copper grade higher than 0.208%, with an acid solubility index higher than 43% and a cyanide solubility index higher than 17% are leached. In Toquepala, the copper sulfides cutoff grade is 0.153% and therefore material with a total copper grade between 0.153% and 0.300% are leached.