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Open-pit mining is a large-scale extraction method which is centered on near-surface ore bodies and extracting vital metals and minerals from these ores. This article explains what open-pit mining is and outlines the process by discussing the potential advantages of open-pit mining. At the same time, we wish to address the substantial environmental and social challenges associated with this mining method.
What is open-pit mining?
Open-pit mining – also called open-cast or open-cut mining – extracts near-surface ore bodies by progressively expanding a terraced pit, stripping away waste rock to expose and remove the ore with large machinery. Because the work is carried out in the open air rather than underground, operations can achieve great scale and productivity, but they also leave some of the largest human footprints on Earth.
Interested in learning more about underground mining? Read here
Situations when open-pit mining may be necessary
An orebody is considered for open-pit development when three conditions align:
- When the deposit is shallow and laterally extensive
- When commodity prices can support a low stripping ratio: the volume of waste that must be removed per tonne of ore
- When enough land is available for waste dumps, haul roads, and processing infrastructure
Feasibility studies therefore combine geological modelling, pit-slope stability analysis, cost curves, and social-environmental baselines to decide whether the net present value of mining outweighs the ecological debt that will accrue over decades of operation and closure. Engineers prefer open-pit mining to other methods because it is cost-effective and flexible, there are safety advantages to this method, and it proves to have a higher ore recovery.
One should also consider the ore type
Open-pit mining is also ideal for certain ore types, including:
- Low-grade, high-volume ores (e.g., copper, gold, iron)
- Shallow, horizontal, or gently dipping ore bodies
- Soft or moderately hard rock formations
Our two cents on the use of open-pit mining
The growing demand for copper, lithium, iron ore, and rare earth elements – critical for the global energy transition – is driving the mining industry to explore deeper and more remote ore bodies. Many of these are in ecologically sensitive biomes, raising new environmental and logistical challenges.
As a result, the future of open-pit mining will be shaped by three converging trends:
- The emergence (and use) of environmentally friendly techniques: The deployment of autonomous, low-carbon vehicle fleets and trolley-assisted haul roads is reducing both diesel use and labor intensity, shrinking the industry’s environmental and operational footprint.
- The use of pit-to-plant digital twins: This enables the optimization of blasting designs and processing routes, which helps minimize waste and inefficiencies.
- Environmental, social, and governance (ESG) compliance: There is increasing ESG scrutiny, where stakeholders now expect mining companies to account for water usage, carbon emissions, and biodiversity impacts. This shift is making marginal deposits less economically viable while favoring projects that can demonstrate net-positive environmental and social outcomes.
Ultimately, whether open-pit mining remains socially and politically acceptable will depend less on the engineering achievements within the pit itself, and more on how responsible mining companies design, operate, and decommission these massive excavations.
Advantages of open-pit mining and reasons why engineers prefer it
Cost-effectiveness
- Lower operational costs: Compared to underground mining, open-pit mining generally requires less infrastructure and specialized equipment.
- High productivity: Large-scale machinery can operate efficiently, moving vast quantities of rock and ore with fewer workers.
- Easy access: Open-pit designs allow quick and continuous access to mineral deposits without the need for complex tunneling.
Safety advantages
- Reduced risk to workers: Open-pit mines are generally safer because they avoid the dangers of cave-ins, rockfalls, or ventilation failures common in underground mining.
- Better ventilation and visibility: Working in the open means no artificial ventilation systems are needed, and hazards are easier to detect.
Flexibility in design and operations
- Easier scaling: Pit sizes can be expanded as needed to accommodate more ore extraction or changes in demand, at least until the deposit becomes too deep.
- Selective mining: It’s easier to control the extraction of high-grade ores, reducing waste and improving ore quality.
Higher ore recovery
- More complete extraction: Since access is not limited by tunnels or shafts, more of the ore body can be mined and processed.
- Less dilution: With proper planning, ore mixing with waste rock is minimized, leading to better quality ore for processing.
Potential environmental impacts of doing open-pit mining
While open-pit mining has many advantages, it also comes with environmental and social challenges. These limitations must be taken seriously when planning for a mining project and when carrying out the drilling process.
Large surface disturbance and landscape alteration
Open-pit mining transforms a natural landscape into a large, terraced crater – sometimes several kilometers wide and hundreds of meters deep. This alteration has wide-ranging effects:
- Topography is permanently modified: Hills, forests, and natural valleys are removed or reshaped
- Creation of artificial landforms: Waste rock dumps, tailings piles, and access roads add to the changes in natural land contours
- Visual impact: The pits are often visible from great distances, reducing the aesthetic and recreational value of the area
Habitat destruction and biodiversity loss
The clearing of large areas of vegetation and soil directly affects local ecosystems:
- Deforestation: Trees and undergrowth are removed, eliminating food sources and shelter for wildlife
- Displacement or extinction: Species that cannot migrate or adapt to new environments may die out locally
- Fragmentation: The pit and associated infrastructure create barriers that disrupt wildlife migration and breeding patterns
Soil degradation and erosion
Mining removes not only vegetation but also the topsoil that supports plant life:
- Loss of fertile soil: Makes future revegetation or agricultural use difficult without costly rehabilitation
- Erosion: Exposed slopes and loose material increase susceptibility to water and wind erosion
- Sedimentation: Runoff from these areas can clog rivers, wetlands, and lakes with silt, harming aquatic life
Hydrological changes
Open-pit mining can alter both surface and groundwater systems:
- Lowering of water tables: Dewatering (pumping water out of the pit) can dry up nearby wells and wetlands
- Altered drainage: Natural streams may be diverted or cut off entirely
- Pollution risk: Exposed minerals in waste rock can leach into surrounding water systems (e.g., acid mine drainage)
Post-mining land use challenges
Once operations cease, restoring the land is complex and expensive:
- Rehabilitation is rarely full restoration: Often the land becomes suitable only for limited uses (e.g., grazing or tourism)
- Pits may become toxic lakes: Abandoned pits can fill with water that turns acidic and metal-rich
- Long-term instability: Waste piles may slump or erode, creating safety and environmental hazards
A historical perspective on open-pit mining
Humanity has quarried shallow deposits for millennia. Early miners identified mineral-rich areas through natural outcrops, discoloration in rocks, or by following riverbeds where metals appeared. Shallow deposits were dug up with ancient tools, and (mostly native) metals were then extracted for smelting and smithing.
As the use of metals became more common, these primitive mines had to become deeper and larger, however, the predominant use of hand tools to excavate the rock meant that deposits needed to be quite shallow for them to be dug up from the surface. Once the deposit went deeper, it was much more feasible to dig mining shafts instead. That made underground mining rather popular historically, though never quite more so than open-pit mining.
Emergence of technology
Throughout ancient and medieval times, open-pit mining has largely stayed the same, though specialized tools were developed, the quality of the tools was improved, and the employment of draught animals became common. But in modern times, truly «game-changing» breakthroughs were introduced, with steam power, dynamite, and railways.
Not only did it become possible to clear up entire mountains rather quickly with explosives to reach the deposits, but steam machines could help clear out the waste rock, and trains could quickly transport it to processing plants. As such, the definition of «shallow deposit» was greatly expanded, and open-pit mining became the vastly dominant form of mining, with over 80% of mining work today being done in open pits.
Further developments in the 21st century saw low-carbon vehicles being introduced, as well as trolley-assist haul roads, to reduce fossil fuel usage. Furthermore, machine learning began to be utilized by creating virtual models of the entire mining process, to further optimize blasting strategies and processing workflows.
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