Contents
Underground mining extracts ore through tunnels and shafts dug beneath the Earth's surface, rather than by excavating an open pit. It is one of two dominant mining techniques that are used for mineral exploration. It involves creating tunnels and shafts underground and extracting ore deposits from here.
In short
- Precision Extraction: Underground mining accesses deep, narrow, or steeply dipping orebodies with a significantly smaller surface footprint than open-pit mining.
- Capital & Technical Intensity: While it requires higher initial capital expenditure and specialized geotechnical engineering, it is often the only viable method for high-grade or deep-seated deposits.
- Modern Transformation: Automation, real-time AI monitoring, battery-electric vehicles (BEVs), and advanced directional drilling are reshaping safety, efficiency, and resource confidence.
- ESG Focus: Environmental, Social, and Governance (ESG) performance and minimal surface disruption are now decisive factors in securing a social license to operate.
What is underground mining?
Underground mining is the process of extracting high-value minerals and ores located deep beneath the Earth’s surface by constructing networks of vertical shafts, inclined ramps, and horizontal tunnels.
Unlike open-pit mining which removes vast amounts of surface rock to create open craters underground mining targets deep, narrow, or steeply dipping orebodies with surgical precision. It is the primary method used to recover critical minerals essential for global infrastructure and energy transitions, including nickel, copper, cobalt, rare earth elements (REEs), and gold.
Learn more about Rare earth elements (REE) in our dedicated technical guide.
Surface mining vs. underground mining: When is underground mining selected?
A deposit is considered for underground mining when the orebody is deep, narrow, or located beneath sensitive land areas such as urban zones, protected ecosystems, or major infrastructure.
Geological and Financial Decision Factors
- Depth of the Orebody: Ideal for deep, narrow, or steep high-grade deposits to avoid excessive surface waste stripping.
- Deposit Geometry and Grade: High-grade ores justify the higher cost of underground extraction, especially when the mineral content is dense and concentrated.
- Surface Footprint: When land access is limited – due to ownership, regulations, or ecological sensitivity – underground mining minimizes surface disruption.
Benefits to doing underground mining
Lower surface impact
- Minimal landscape alteration: Because much of the infrastructure is below ground, the visual and ecological footprint is far smaller than in open-pit operations.
- Preservation of surface land use: Useful in agricultural or urbanized areas where continued surface activity is desirable.
Access to deep deposits
- Feasible at great depths: Underground methods can extract ore located hundreds or even thousands of meters below ground level – far deeper than practical open-pit limits.
Selectivity and precision
- Targeted extraction: Precision drilling and blasting allow for the careful extraction of ore, minimizing dilution from surrounding rock.
- Reduced waste rock volume: As only the ore is typically removed, less waste needs to be managed.
Long-term production potential
- Expandable networks: Underground tunnels and stopes can be extended incrementally, making underground mines adaptable to changing geological understanding and commodity prices.
Limitations and challenges
While underground mining can be more sustainable on the surface, it brings unique operational and environmental challenges.
Safety risks
- Cave-ins and ground failure: Structural integrity of tunnels must be constantly managed to prevent collapses.
- Air quality: Poor ventilation can lead to buildup of toxic gases (e.g., methane, carbon monoxide), requiring continuous airflow systems.
- Seismic activity: In deep or geologically active zones, mining can trigger or be affected by underground tremors.
High costs
- Capital-intensive: Shaft sinking, ventilation, dewatering systems, and safety infrastructure add significant upfront and ongoing costs.
- Labor demands: Requires more personnel per tonne of ore compared to open-pit mining
Limited ore recovery
- Access constraints: Not all ore can be safely or economically reached, especially near support pillars or weak rock zones.
- Dilution risks: In complex deposits, unintended mixing with surrounding rock can reduce ore quality.
Water and heat management
- Flooding risk: Groundwater ingress is common and requires constant pumping.
- Heat stress: Deeper mines often exceed 40°C, necessitating powerful cooling systems for human operation.
Surface subsidence
- Ground movement: Over time, underground voids may collapse, causing land above to sink or crack – especially problematic in populated areas.
Outlook on underground mining
As global demand accelerates for minerals essential to renewable energy technologies, electronics, and modern infrastructure – such as nickel, cobalt, rare earth elements, and gold – mining companies are increasingly turning to underground methods.
Many of these critical minerals are found in deeper, more geologically complex orebodies that are often located in remote or environmentally sensitive areas. In such cases, open-pit mining becomes impractical or socially unacceptable, making underground mining a crucial way of unlocking these strategic resources.
Modern Innovations: Automation, AI, and Directional core drilling
The future of underground mining is being shaped by a number of transformative trends.
Automation and Tele-Remote Operations
Automation and robotics are at the forefront of modern mine engineering. Driverless haul trucks, autonomous drilling rigs, and tele-remote loaders remove personnel from high-risk production zones, allowing operators to run machinery efficiently from surface control stations.
Real-Time Monitoring and Artificial Intelligence (AI)
Underground operations are increasingly equipped with integrated IoT sensor networks that track rock stress, air quality, water inflows, and equipment health in real time. AI algorithms analyze these data streams continuously, enabling predictive maintenance, dynamic workflow optimization, and early warning for geotechnical risks.
All-electric mining
To meet decarbonization targets, mining companies are replacing traditional diesel fleets with Battery-Electric Vehicles (BEVs). Low-emission electric equipment significantly reduces underground heat generation, lowers toxic exhaust, and drastically cuts surface ventilation energy requirements.
ESG considerations
ESG considerations now play a central role in the approval and long-term success of underground mining ventures. Projects must demonstrate sensitivity to community concerns, cultural heritage, and groundwater systems. Transparent stakeholder engagement and inclusive planning are no longer optional – they are essential prerequisites for gaining trust and ensuring continued access to high-value deposits
The role of directional drilling in deep mining operations
Before underground mine development begins, exploration geologists must map complex, deep orebodies with surgical accuracy. Traditional straight diamond drilling often requires constructing numerous surface drill pads, driving up exploration costs and environmental footprints.
Modern Directional Core Drilling (DCD), such as Aziwell’s AziDrill technology allows exploration teams to steer a single drill hole into multiple target branches deep underground.
- Multiple Branch Holes: Multiple target branches can be initiated from a single parent hole, reducing the need for multiple surface drill sites.
- Target Accuracy: Precision steering allows geologists to intersect thin or complex mineral structures at optimal angles, securing higher-quality core samples for resource estimation.
Read our full article on Directional core drilling to learn more.
In summary, while underground mining involves greater technical complexity and financial commitment, it offers a vital route to accessing the critical minerals that are needed in the global energy transition and digital economy. Its future will depend not only on engineering ingenuity but also on how responsibly and sustainably companies navigate the challenges of working beneath the Earth’s surface.
A historical perspective on underground mining
Underground mining techniques date back thousands of years. Early miners in Egypt, Greece, and Rome used primitive hand tools to follow ore veins underground, with firesetting as one of the earliest forms of hard rock mining. Firesetting involved heating rock then quenching it with water to crack it. The labor was hard and dangerous, yet it allowed access to richer, more concentrated ores than those available at the surface.
In the Middle Ages, miners developed vertical shafts and timbered tunnels to reach deeper deposits. Water-powered hoists and ventilation shafts improved productivity and safety. By the Industrial Revolution (18th-19th century), gunpowder and later dynamite allowed deeper and faster excavation. Steam engines replaced human and animal power for hauling ore and draining water.
By the 20th century, mechanized drilling, rock bolting, and electric locomotives had transformed operations underground. Today's mines often resemble small cities — running on electrified haulage, automated loaders, and tele-remote drilling systems that boost both safety and efficiency.
Take advantage of our advanced directional drilling technology
Aziwell is a leading provider of directional drilling solutions and offers service and software products for directional drilling. At the heart of this is our advanced borehole steering technology, which reduces environmental footprint through fewer drill pads, operational time and CO₂ emissions. Our directional drill, AZIDRILL, is precise, does not require special rods or rigs, and has no depth limitations.
Frequently asked question about underground mining
What is the main difference between underground mining and open-pit mining?
Open-pit mining excavates minerals near the surface by stripping away all overburden rock to create a large open crater. Underground mining accesses deep orebodies by constructing a network of shafts, ramps, and tunnels beneath the Earth's surface, extracting the mineral with minimal surface land disturbance.
Is underground mining safer today than in the past?
Yes. Advances in ground support engineering (rock bolting, shotcrete), real-time micro-seismic monitoring, automated ventilation control, tele-remote equipment, and strict safety regulations have significantly reduced underground operational risks compared to historical practices.
Which minerals are mined underground?
Underground mining is commonly used for high-grade or deep-seated metals including gold, silver, copper, nickel, zinc, platinum group metals, and rare earth elements (REEs), as well as industrial minerals, coal, and potash.
What dictates the choice of an underground mining method?
The selection of an underground mining method (such as Room and Pillar, Sublevel Stoping, or Block Caving) depends on the depth, geometry, and inclination of the orebody, the mechanical strength of the ore and surrounding host rock mass, and overall operational economics.
