Rio Algom uses solution mining at three projects

In its bid to develop low-cost and efficient mining processes for the future, Rio Algom (TSE) has three projects under way that make use of innovative techniques such as solution mining and in situ leaching. Solution mining is essentially a process whereby minerals such as potash, uranium or copper are dissolved out of the host rock formations underground and then transported by solutions to surface processing plants.

This mining method may greatly reduce or eliminate the need for drilling, blasting and transportation of crude ore, and it may be applied to either new deposits or mined out portions of conventional mines where conditions permit.

At the company’s potash mine in Saskatchewan, for instance, nearly 700 km of flooded mine workings have been converted to solution mining. The process involves injecting and circulating a brine solution through the flooded workings where it is heated and absorbs the potash. The solution is then pumped to surface where it cools in a series of settling ponds and potash precipitates out to be recovered by a dredge.

In situ leaching of uranium is being studied at the company’s properties in Wyoming where the potential for solution mining development is under consideration.

Although few uranium properties are suitable for in situ leaching, the technique has lower capital and operating costs because it not only replaces conventional mining techniques, but bypasses a large portion of the traditional milling process.

Where the technique is practical, an environmentally benign solution is pumped down an injection well and flows through the deposit to dissolve uranium. The uranium- bearing solution is pumped to surface, and the metal recovered.

On a third Rio Algom project, in Chile, solution mining is being considered for the company’s Cerro Colorado copper deposit which has the potential to become a long-term, low-cost producer. Rio is evaluating copper extraction using bacterial leaching of conventionally mined ore stacked in piles or heaps. The pilot studies, which tested crushing size, pile height and other variables, indicated a potential recovery of more than 80%, as well as cost advantages over traditional recovery methods.