Minera Escondida

Minera Escondida (which means 'hidden' in Spanish) is a mining company that operates two open pit copper mines in the Atacama Desert, 170 km southeast of Antofagasta in northern Chile. It is currently the highest producing copper mine in the world. Its 2007 production of 1.483 million tons of the metal was worth US$ 10.12 billion, mainly as metal in concentrate, but some as cathode, and was 9.5% of world output and 26% of Chilean production, according to the US Geological Survey's preliminary estimates of 2007 world mine output.

It is so called because the main orebody does not outcrop on the surface, but is 'hidden' by hundreds of metres of practically barren overburden. The lower open pit in the satellite image on the right is the main Escondida mine, but the upper two are Barrick Gold's Zaldívar mine. The second Escondida open pit, Escondida Norte, had not been established when the image was taken, but is now immediately to the right (east) of the larger Zaldívar pit.

Escondida produces mainly copper concentrates, which are piped as a slurry down to the port of Coloso, where they are dewatered before shipping, and a smaller proportion of cathode copper from the leaching of both oxide and low grade sulfide ore. It also produces gold and silver.

The mine is owned 57.5% by BHP Billiton, 30% by Rio Tinto, 10% by JECO, a Japanese consortium headed by Mitsubishi and 2.5% by JECO 2, a consortium with the same owners but different shares. It is managed by a seven-man Owner's Council designated by the four owners. At present, Escondida is the largest foreign investment in Chile, with a cumulative investment of US$5.64 billion at the end of 2006.

In 1978, J David Lowell proposed an exploration program along the porphyry copper belt between Chuquicamata in the north and El Salvador in the south. Minera Utah de Chile and Getty Mining (Chile) formed a joint venture to carry it out. On March 14 1981, 'Pozo 6' the last scheduled borehole in the program, hit 52 metres of 1.51% copper at a depth of 240 metres and discovered the main Escondida orebody. More holes were drilled to delineate the orebody and a shaft was sunk to provide bulk samples for metallurgical testing. Construction of the mine started in 1988, which including the stripping of over 180 million tonnes of waste to get to the orebody.

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