At Mount Lyell Mine underground sub-level caving mining is carried out at 900 meters below the original surface (450 meters below sea level). The mine production is about 2.6 million tonnes per annum of copper ore at 1.3% copper grade. The copper ore also contains 0.3 grams gold and 3 grams silver per ton of ore.

The Main Decline extends 6.5 km from surface to 900 meters below surface.

Mined ore is transported by trucks to underground primary crusher and hoisted to surface by an automatic shaft.