If you ask anyone what mining looks like to them, they will likely describe a large hole complete with big yellow dump trucks and excavators moving tonnes of dirt – an ‘open cut’ mine, or dark underground tunnels filled with workers wearing helmets and headlamps – an ‘underground’ mine. These types of mines have historically been – and are still – the most common types of mines found across the world. However, there are others – one of which is in situ recovery or ISR mining, a technique that has been used since the 1970s in Australia, the United States, Kazakhstan, China, and Russia to mine potash, salt, uranium, and copper.

What is in situ recovery mining?

• In situ, recovery mines use fluid to recover minerals from the ground without digging and moving tonnes of earth as in an underground mine.
• It involves pumping lixiviant (mining solution) underground to mobilise valuable minerals from the ground. The fluid is then pumped back to the surface and sold as the rest of the solution is sent back through the rock to recover more minerals. Engineers continue this process until there are no longer minerals and the mine is closed. 
• Depending on the properties of the mineral deposit, the fluid that will most effectively liberate the minerals may be either acidic or alkaline. Figure 1 shows the in situ recovery process, showing the location of the mineral deposit, the circulation of fluids, and the wells placed around the mining zone that demonstrate control of the mining process.

Because in situ recovery mining involves the circulation of fluid rather than the movement of rock, the surface is not disturbed, and there is less noise, dust, and vibration that is associated with open-cut or underground mining.

Why then is in situ recovery only used for some mines?

Put simply, all mineral deposits are located in different environments, and in situ recovery is only a viable mining method in some situations. In situ recovery mining is appropriate in situations where:

• Water moves freely throughout rocks and the soil. 
• minerals can be mixed into water and pulled out of the ground. 
• Minerals can be recovered from solution.
• Such solutions can be contained in the local environment
• The process can occur with limited damage to the environment. 
• the overall process can be undertaken economically.

Studies could take years of investigation, including drilling into and around mineral deposits, sampling, and mapping groundwater in and around the local area, with detailed lab work to evaluate whether a site is suitable for the in situ recovery method. If preliminary studies are positive, a carefully regulated trial is usually undertaken to validate the results of those investigations and to prove that the deposit can be effectively and safely mined before there is any decision to allow mining to proceed.

The South Australian and Commonwealth governments have been regulating in situ recovery mining operations since the late 1990s and are a leading contributor to global regulatory practice for the development, operation, and closure of in situ recovery mining operations, as described in Australia’s in situ recovery uranium mining best practice guide. 

Whilst to-date in situ recovery is commonly only used in Australia for mining uranium, and in large-scale operations across the globe for mining potash, salt, uranium, and copper, global interest is growing in its use for other minerals such as nickel, silver, zinc, and cobalt. Research organisations such as Australia’s CSIRO are partnering with the government and industry to explore further opportunities for the safe and successful use of in situ recovery mining around the world.

IN-SITU Mining at COBRE Ltd. 

Cobre Ltd. (ASX: $CBE) has achieved a significant milestone in its Ngami Copper Project (NCP) located in Botswana's Kalahari Copper Belt. Not only has it discovered high-grade copper, but the company also checked the box for In-Situ copper recovery. Cobre has also completed the initial phase of a program testing the feasibility of an In-Situ Copper Recovery (ISCR) process. 

1. Results say that the project has over 40 kilometres of drilled test copper-silver mineralisation with a consistent grade and an exploration target exploration target that could deliver substantial returns to shareholders.
2. The company is feasible for the In-situ process at the site.

For Cobre In-situ methods will potentially lower costs, and reduce its environmental impact, safer working conditions, and suitability for specific deposits. Can effectively extract copper from deep or fragmented ore bodies.

The environmental advantages are clear, including minimal noise, dust, or greenhouse gas emissions, along with minimal visual disturbance. In addition, it also lowers capital and operating costs while creating a safer environment for mine workers. Too bad not all mines can operate without moving a rock.