Mining Methods for Critical Minerals
Mining is the first major capital-intensive stage in the critical minerals supply chain. The choice of method depends on deposit depth, geometry, grade, and mineralogy - and nearly every known technique finds application somewhere in the critical minerals value chain.
US average permitting time
7–10 yrs
Can exceed 15 with legal challenges
ASM share of world cobalt
15–30%
Artisanal mines in DRC
Brine evaporation cycle
12–18 mo
Lithium Triangle salars
Ionic clay REE source
Jiangxi
Primary supply of heavy REEs
For critical minerals, the diversity of deposit types means that nearly every known mining technique finds application somewhere in the value chain. Lithium is extracted from both hard-rock mines and brine evaporation ponds. Rare earths are recovered from open pits in carbonatites and through in-situ leaching of ion-adsorption clays. Cobalt is mined underground in the copper-cobalt belt of the Democratic Republic of Congo and as a byproduct of nickel laterite operations in Indonesia and the Philippines.
Mining Methods at a Glance
Each method has a distinct cost profile, surface impact, and range of minerals it can economically extract.
Method
Key Minerals
Best For
Trade-off
Example
Open-Pit
Rare earths, lithium (hard-rock), copper, cobalt
Large, near-surface, lower-grade ore bodies
Low cost per tonne; large surface footprint and waste volumes
Bayan Obo (China), Greenbushes (Australia)
Underground
Platinum group metals, cobalt, deep copper, hard-rock lithium
Deep or narrow ore bodies uneconomic to strip
Higher cost; smaller footprint but complex ventilation and ground support
Bushveld Complex (South Africa), Kamoa-Kakula (DRC)
In-Situ Recovery (ISR)
Uranium, ionic clay REEs, copper (trials), lithium (trials)
Permeable ore bodies where fluid injection is practical
Low surface disturbance; groundwater contamination risk if poorly managed
Ionic clay REE deposits in Jiangxi Province, China
Brine Extraction
Lithium, potash, boron
Continental salar brines in arid high-altitude environments
12–18 month evaporation cycle; water-stressed settings create community conflict
Atacama salar (Chile), Salar de Uyuni (Bolivia)
Artisanal & Small-Scale (ASM)
Cobalt, gold, tin, tantalum, coltan
Shallow, high-grade, informal workings
Low capital; persistent safety, child labor, and environmental risks
Kolwezi region, DRC (15–30% of world cobalt supply)
Open-Pit Mining
Open-pit mining is the most common method for large, near-surface critical mineral deposits. The process involves removing overlying waste rock (overburden) to expose the ore body, which is then drilled, blasted, loaded onto haul trucks, and transported to processing facilities. Open-pit mines can achieve enormous scale: the Bayan Obo rare earth mine in Inner Mongolia, the world's largest rare earth operation, has been in continuous production since 1957.
The advantages of open-pit mining include lower per-tonne extraction costs, higher production rates, and greater operational flexibility. However, the environmental footprint is substantial - large volumes of waste rock and tailings, altered surface hydrology, and lasting landscape disturbance. Progressive rehabilitation, including backfilling, revegetation, and water treatment, is now a regulatory requirement in most jurisdictions, though enforcement varies considerably.
Underground Mining
When deposits extend to greater depths or are too narrow for open-pit extraction, underground methods are employed - room-and-pillar, sublevel stoping, block caving, and cut-and-fill techniques. Underground mining is essential for accessing the deep copper-cobalt deposits of the Central African Copperbelt, the PGM reefs of South Africa's Bushveld Complex, and numerous hard-rock lithium pegmatites.
Underground operations face higher per-tonne costs due to ventilation, ground support, underground haulage, and dewatering systems. The Kamoa-Kakula copper-cobalt project in the DRC, developed by Ivanhoe Mines, represents a new generation of large-scale underground critical mineral operations that aim to combine high production rates with modern safety and environmental standards.
In-Situ Recovery (ISR)
ISR involves injecting a leaching solution into the ore body through injection wells, dissolving target minerals underground, and pumping the pregnant solution to the surface for processing. It is the dominant method for uranium and is increasingly evaluated for lithium, rare earths, copper, and nickel.
ISR is particularly significant for ionic clay rare earth deposits in southern China and Myanmar, where dilute ammonium or magnesium sulfate solutions desorb rare earth ions from clay minerals. These deposits are the world's primary source of heavy rare earths - dysprosium and terbium - critical for high-performance permanent magnets. However, ISR of ionic clays has historically caused groundwater contamination and soil degradation, prompting Chinese authorities to consolidate operations and tighten environmental standards.
Why heavy REE supply is concentrated in China
Ion-adsorption clay deposits hosting the heavy rare earth elements (dysprosium, terbium, holmium) are almost exclusively found in the weathered granites of Jiangxi Province and adjacent regions. The ISR method they require is technically straightforward but environmentally sensitive. No comparable formation outside China has been brought to commercial production at scale, making this a single-point dependency in the global magnet supply chain.
Brine Extraction and Direct Lithium Extraction
Lithium production from continental brines, concentrated in Chile, Argentina, and Bolivia, pumps lithium-rich brine from underground aquifers into large evaporation ponds. Solar energy drives progressive concentration over 12 to 18 months; the concentrated brine is then processed chemically to produce lithium carbonate or lithium hydroxide. This method offers low energy costs but requires vast land areas and draws opposition from local communities concerned about water impacts on fragile high-altitude ecosystems.
Direct Lithium Extraction (DLE) technologies, using selective adsorption, ion exchange, or membrane processes, are under active development as an alternative that avoids large evaporation ponds. DLE promises faster extraction times, higher recovery rates, and reduced water consumption - potentially unlocking brine resources previously considered uneconomic.
Companies developing DLE technology
Environmental and Social Considerations
Mining for critical minerals carries significant environmental and social impacts that vary by method, scale, and jurisdiction. Acid mine drainage, tailings dam failures, deforestation, biodiversity loss, and water depletion are well-documented risks. The catastrophic tailings dam failures at Samarco (2015) and Brumadinho (2019) in Brazil have heightened scrutiny of tailings management across all mining sectors.
The artisanal cobalt problem
An estimated 15–30% of the world's cobalt supply originates from artisanal and small-scale mining (ASM) in the DRC, where child labor, hazardous working conditions, and lack of safety equipment remain persistent problems despite industry initiatives.
Responsible Minerals Initiative
Third-party audit framework for smelters and refiners
Fair Cobalt Alliance
Supply chain formalisation and community support programs
OECD Due Diligence Guidance
Government-backed standard for responsible minerals sourcing
As demand for critical minerals grows, ensuring that extraction meets acceptable environmental and social standards is both an ethical imperative and a regulatory requirement that increasingly affects project financing and market access.
Permitting and Development Timelines
The time required to take a project from discovery to production is a major constraint on supply responsiveness. Timelines vary dramatically by jurisdiction.
United States
7 – 15+ years
Canada
5 – 8 years
Australia
5 – 8 years
DRC / Central Asia
1 – 3 years
The United States, European Union, Australia, and Canada have all introduced legislative and regulatory reforms aimed at accelerating mine approvals for strategic mineral projects. These reforms must balance the legitimate need for speed with thorough environmental and social impact assessment - a tension that will define the politics of critical mineral supply for decades to come.
Continue Along the Supply Chain
Exploration and Resources
How deposits are discovered and classified before mining begins.
Beneficiation and Concentration
The crushing, grinding, and separation steps that upgrade ore after extraction.
Traceability and Certification
How responsible sourcing standards address mining-stage social and environmental risks.
Recycling and Circularity
How recycling can reduce demand pressure on primary mining of critical minerals.