How deep can open-pit mines become?

Open-pit mines do not have a fixed maximum depth; rather, their depth is determined by economic viability. As a pit is deepened, the volume of waste rock that must be stripped to uncover the ore increases. Mining ceases when the cost of removing this waste rock exceeds the revenue generated by the recovered ore, a threshold known as the break-even stripping ratio.1

While there is no universal limit, the deepest open-pit mines in the world currently exceed 800 metres (2,600 feet) in depth.2

As pits reach these significant depths, operators must carefully manage the stability of the pit walls, which is influenced by the strength of the rock mass and the slope angles. Because of the increasing costs and logistical challenges associated with depth—such as the need for specialized transport systems like belt conveyors—many operations eventually transition to underground mining when the surface stripping requirements become prohibitive.132