openpit

Open-pit mining, also written open pit, is a surface mining technique used to extract rock or minerals from an ore body that is near the surface. The operation removes overburden and waste rock to access ore, creating a pit that expands gradually through benching and hauling. It is the most common method for bulk mining of relatively shallow, horizontally extensive orebodies, and contrasts with underground mining.

Design and operation involve determining pit limits through optimization of economic factors and safety constraints. The pit is excavated in levels, or benches, with a typical bench height of 10 to 20 meters. Equipment such as blasting crews, shovels or excavators, and large trucks or conveyors move ore and waste. The stripping ratio (waste to ore) and cut-off grade govern sequences and life of mine.

Economic considerations include ore grade, metal price, recovery, and capital and operating costs. Environmental and safety concerns cover land disruption, dust, noise, water management, erosion, and potential acid rock drainage. Rehabilitation plans aim to restore land forms and ecosystems after pit closure. Proper design reduces waste, controls geotechnical instability, and manages water inflows.

Open-pit mining is widely used for copper, gold, iron ore, coal, and other bulk commodities. It requires relatively flat terrain and ore near the surface. While cost-effective for large-tonnage deposits, it also imposes long-term land-use impacts and requires ongoing monitoring and reclamation.