By Ellsworth Dickson
In-situ mining, also known as solution mining, does not utilize traditional drilling, blasting, hauling, milling and waste rock disposal used in underground or open pit mining.
Instead, the in-situ mining process involves drilling wells into the orebody and injecting a solution that dissolves the valuable metals that are then pumped to surface.
Since expensive conventional mining methods (open pits and underground workings) and related processing facilities are not needed, mining costs are lower, making in-situ mining suitable for ordinarily uneconomic orebodies economically viable – typically copper, uranium and gold deposits.
In addition, in-situ mining offers the advantages of no noise, no dust, and no abandoned open pit mines, tailing ponds and dams. In-situ mining can also achieve higher recovery rates than traditional mining methods.
However, in-situ mining is only a suitable mining method under certain conditions, including porous rocks that allow the mining solution to dissolve the target metal.
Another type of in-situ mining is bioleaching, a process whereby microorganisms are used to dissolve the minerals in the orebody. The solution is then pumped to the surface for recovery. The tiny bacterial organisms “eat” the metals of interest. The resulting solution is then pumped to the surface. No cyanide is used as in traditional heap leach mining.
Another in-situ mining method is hydrothermal mining that involves heating the orebody to high temperatures to dissolve the minerals. The solution is then pumped to the surface for recovery.
It is important for long-term monitoring of the mining solution and the surrounding rock formations to ensure that the mining process is safe and effective.
There are a number of mining companies around the world that use in-situ mining techniques to extract minerals and metals. Some examples include Taseko Mining Ltd. [TKO-TSX, LSE; TGB-NYSE American] that uses in-situ mining to extract copper at its Florence project located midway between Phoenix and Tucson near the community of Florence, Arizona.
Development of the project is being performed in two phases – the first phase is a production test facility, which is followed by the second phase commercial facility.
Uranium Energy Corp. [UEC-NYSE American; U6Z-FSE] is employing low cost, environmentally friendly, in-situ recovery or ISR mining technology at its fully licensed projects, including Palangana (Texas), Burke Hollow (Texas), and Reno Creek (Wyoming) uranium projects.
Energy Fuels Inc. [EFR-TSX; UUUU-NYSE-American] owns and operates the Nichols Ranch in-situ recovery mine and processing facility. Nichols Ranch is located in the productive Powder River Basin district of Wyoming and has a total licensed capacity of 2 million pounds of U3O8 per year.
Heathgate Resources Pty. Ltd. operates the in-situ Beverly and Beverly North uranium mines approximately 550 km north of Adelaide, Australia.