Opencast/Opencut/Open-pit Mining

Surface mining, in which the ore is excavated from a pit, has been used extensively in Australia, Canada, Papua New Guinea and the United States in recent years for the recovery of low grade finely disseminated oxide ores.

Newmont Gold's opencast Gold Quarry on the Carlin Trend in Nevada
(Credit: courtesy Newmont Gold Company)

Depending on the geometry and depth of the orebody, the advantage of open-pit, as opposed to underground, mining is that it is usually easier, cheaper and quicker to bring into production. Open-pit mines in Nevada and in Western Australia have often been brought on-stream within a year at a cost far below the development of underground mines and in both regions account for virtually all gold production.

Open-pit deposits often have a relatively short life-span (on average, four to five years), after which it may become necessary to move to underground mining techniques to access deeper ores (if they are available and economic). However, the continued identification of new surface deposits, such as those along the Carlin Trend in Nevada, USA, often provides replacement ore reserves.

Heap leaching and carbon-in-pulp recovery have also resulted in the mining of large tonnage, low grade, near surface gold deposits. Almost eighty per cent of all gold production in the United States comes from open-pit mining.