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:: Re-treating Diamond-bearing Dumps
As part of the new partnership model introduced at the start of the year (click here for story), De Beers has involved Bateman in a number of projects to recover diamonds from tailings dumps at its older mines.
These dumps contain reject material deposited over many years when the diamond-recovery processes were not as efficient as they are today and are now known to contain meaningful amounts of small diamonds. The possibility, however, of finding larger stones too is not excluded.
James Nieuwenhuys, Bateman General Manager, Diamonds, reveals that studies are being conducted on about a dozen different diamond-recovery routes which could be applied to the reprocessing of dumps, the objective being to have available a suite of processes applicable to all kinds of dump materials and to contain dump-reprocessing costs to an absolute minimum.
In respect of milling, the partnership will be exploring a combination of Western and Russian technologies, arising out of testwork undertaken by Bateman a few years ago in Siberia for a large diamond exploration, mining and marketing company in the Russian Federation.
The key to the milling technology is the slow mill speed which minimises diamond breakage. As many dumps are in arid locations, water usage will also have to be minimised. Bateman has entered into agreements with suppliers of novel milling technology, such as cantilever and planetary systems and innovative liners, so these can be evaluated for use in dump reprocessing.
Some of the novel technology is already finding application in current projects Bateman is undertaking with De Beers. At Namdeb's E-Bay diamond-liberation project in Namibia, the wet-crushing system being installed is the first of its kind in the De Beers Group (see Bateman Globe No. 38, November 2003) and enables the plant to treat all potentially viable deposits including clay-rich and very hard cemented materials.
Because of the remote location of many of the dumps and the potential need to relocate the equipment from time to time to other nearby dumps, Bateman is drawing heavily upon its experience with modular-processing plants which will be applied to all the major processes needed for diamond recovery, e.g. crushing, milling, dense-media separation, X-ray recovery, etc.
According to Nieuwenhuys, several factors motivate projects to re-treat old dumps. "There is today a greatly improved understanding of diamond-liberation processes and more effective methods to recover the diamonds are available," says Nieuwenhuys. "At the same time, the kimberlite in the old dumps has weathered extensively during years of exposure to the elements, facilitating the release of any diamonds associated with the kimberlite. Also, the availability of high-quality primary resources is decreasing and diamond producers are on the lookout for additional resources."
"All old diamond mines have such dumps and this includes all the mines in South Africa, Botswana and Namibia," says Nieuwenhuys.
"In South Africa, the newly promulgated Mining Charter, which fosters a 'use-it-or-lose-it' approach to the exploitation of mining resources, is making mining companies take a far more careful look at smaller deposits. Accordingly, Bateman is in discussion with several black economic-empowerment companies aimed at providing the technology and backup required to get these ventures started.
"Further afield, the improving political situation in the Democratic Republic of the Congo (DRC) and Angola is also opening up possibilities there. Sampling programmes in Canada, for which Bateman equipment has been purchased in recent years, are also revealing promising recovery ventures."
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