JOHANNESBURG (miningweekly.com) – South African mines could recover more cobalt if they changed their blasting methods in hard-rock narrow-reef gold and platinum mines, says veteran research commentator Dr RE (Robbie) Robinson.
With the world suddenly taking new cognisance of cobalt because of its use in electric cars and microchips, Robinson believes that hard-rock, narrow-reef miners should waste no time in moving to selected blast mining (SBM), which also facilitates mine mechanisation in confined stopes and boosts overall precious metal recoveries significantly.
“If you can selectively separate the reef part of the underground ore reserve and throw the waste rock aside, the cobalt concentration once that ore reaches the surface is very much higher and becomes easier to recover,” Robinson tells Mining Weekly Online in the attached video interview.
“If you adopt a zero waste, non-toxic philosophy on waste residues, it’s easy enough to recover all that cobalt, while also recovering uranium and quite a number of other elements that have potential value.
“We should be doing this, and it should be started just as soon as we possibly can,” the one-time National Institute for Metallurgy, now Mintek, director advocates, against the background of the current buzz in the cobalt world following the announcement of electric vehicle manufacturer Tesla Motors that it intends building a new $5-billion lithium-ion battery ‘gigafactory’ in the US.
Tesla Motors CEO is Elon Musk, the South African-born Canadian-American entrepreneur, inventor and investor, who was schooled at Pretoria Boys High.
With American companies focusing special research into cobalt recovery as a strategic metal, Robinson is urging South Africa to do better with its squandered cobalt endowment.
US company Applied Materials, a provider of equipment, services and software used for manufacturing semiconductors, sees cobalt as a superior metal encapsulation film, the first important change in materials for microchip wiring in 15 years.
The US technical media wrote of the change that the news was in the word "cobalt" and in the word "wiring", with the headline of another article proclaiming that, “cobalt is the key to future chips”.
By adopting the hydrometallurgical approach to platinum processing, cobalt can be recovered as a high-purity cobalt metal.
Every narrow-reef gold mine has some cobalt in it, but it ends up as one of the toxic elements in acid mine drainage (AMD), which is currently also seldom out of the headlines.
Currently, South Africa’s approach to dealing with AMD is to precipitate it with lime and to put it on a waste dump and as the waste dump gradually weathers and leaches away, the toxic cobalt gets into the streams.
Robinson contends that this need not be so because there are available processes that, in a relatively easy way, can recover that cobalt and produce it as a cobalt oxide, which can be dissolved, electrolysed and made into metal.
Cobalt arises primarily from the Zambian/Democratic Republic of Congo copperbelt and as a by-product of the Bushveld platinum mines in South Africa.
The Chamber of Mines of South Africa says on its website that cobalt is found as a minor element in the base-metal sulphides of the Merensky reef of the Bushveld Igneous Complex (BIC) from which platinum-group metals are extracted, and also in a number of the BICs chromite layers – but makes no mention at all of its presence in gold-bearing reef.
Also used in many other diverse industrial and military applications, the US remains the world’s largest consumer of cobalt, but does not mine cobalt, apart from negligible quantities of by-product cobalt produced as intermediate products from some mining operations.
Robinson has for long contended that the use of SBM, which avoids blasting in the reef layer, would greatly benefit South Africa’s struggling hard-rock precious-metal mines.
SBM add-ons could include underground high pressure roll crushing and mine shaft pressure leaching for uranium and other toxic but saleable metals.
Other countries, including Australia, are waking up to the cobalt opportunity, with a recent study into ASX-listed Broken Hill Prospecting’s New South Wales cobalt deposits pinpointing a new commercial opportunity that could deliver revenues of up to A$381.5-million a year, over a 20-year period.
In addition to the revenues generated from the possibility of a standalone sulphuric acid project near the Broken Hill deposits, the company states that the cobalt value of the project would also be considerable given the cobalt contained in the ore.
Based on a cobalt price of $27 450/t, the model estimated that an additional value of between $822-million and $1.3-billion could be ascribed to the contained cobalt within the deposits.
Broken Hill said that it could be reasonable to assume that between 5 000 t and 6 000 t of cobalt could be produced each year.
In South Africa, SBM can be satisfactorily carried out using shock tubes and delayed detonators, and would be the equivalent of a significant increase in the gold and platinum price as well as potentially also resuscitating Welkom, Carletonville and what is left of the East Rand after the Aurora debacle.
Even East Rand Proprietary Mines has areas that could return to mining, says the former Sentrachem director of mining chemicals and explosives, who has been associated with the South African mining industry since 1949.