Cortona investigate heap leach potential of Black Hill nickel laterite

There is growing interest in nickel heap leach opportunities, and Cortona Resources is just one company advancing this technology. In September 2006, Cortona announced a nickel laterite resource at Black Hill in the North Monger project, 40 km southeast of Kalgoorlie, Western Australia. The inferred resource is estimated to be 30 Mt at 0.64% Ni. The resource was discovered in 1997 and measures more than 3.5 km x 0.4 km, extending to a maximum depth of 40 m. Cortona recently purchased the tenements to the south of the resource, which were never drilled for nickel. The company says “interpretation of geophysical datasets suggests the resource has the potential to continue into this area.”

The resource is located close to suitable infrastructure, being within 30 km of the

Kalgoorlie to Kambalda gas pipeline, 1 km from the Trans Australian Railway, and 4 km from the Mount Monger road that leads to the major mining town of Kalgoorlie. There are also potential sulphur sources nearby for the manufacture of sulphuric acid.

Since announcing the resource, Cortona has been monitoring developments in nickel laterite heap leach technology, which for some ores is being recognised as a viable alternative to the more widely used ‘high pressure acid leach’ (HPAL) technique. The heap leach process is attractive because it not only has the potential for significantly lower capital expenditure than HPAL, but it is also a less complex process.

At this stage there are no producing nickel heap leach operations in Australia. Several projects are under review, including Heron Resources’ Jump Up Dam prospect 150km northeast of Kalgoorlie, where encouraging test results have recently led to a resource drill out. Heron is now conducting a feasibility study of the resource (International Mining Project News, April 15). Elsewhere, European Nickel has commenced construction of a nickel heap leach plant at its Caldag Project in Turkey, with production due to commence in 2008. The latter is featured in IM’s May issue article on bioleaching and hydrometallurgy.

In light of the positive outlook for the heap leaching of nickel, Cortona has engaged the services of Independent Metallurgical Laboratories to conduct test work on the heap leach potential of the Black Hill laterite resource. The work has commenced and will proceed in two stages. The initial stage will firstly characterise the ore before assessing the acid digestion potential via a series of bottle roll leach tests.

If it can be demonstrated that the material is conducive to acid leaching, the test work will then proceed to a more detailed second stage. This will investigate the combined physical and chemical aspects of nickel and cobalt recovery using a column test. Stage 1 is due to be completed by early June 2007, and stage 2, if implemented, should conclude by late October 2007.