The Steenkampskraal rare earths mine, in the Western Cape, owned by developer Steenkampskraal Holdings, aims to establish itself as a building block in a global rare earths supply chain independent of China.
Manufacturers globally are expressing concern over China’s dominance of these strategic elements, while the concentration of rare earths production in China also raises the question of supply vulnerability, says Steenkampskraal Holdings chairperson Trevor Blench.
“The rare-earth resource at Steenkamps- kraal has been confirmed by an NI 43-101 Mineral Resource Estimate as the highest- grade deposit in the world, at an average of 14.4%, with the rare earths grade in some areas as high as 45% total rare-earth oxides.” The recovered grade after dilution will be about 10%.
Most rare-earth deposits globally have an average in situ grade of between 1% and 2%. “When these deposits are mined, the recovered grades will be even less, because the in situ mineralised material will be mixed with material such as waste rock that has little or no economic value,” he notes.
Hard-rock monazite deposits, such as the deposit at Steenkampskraal, generally have much higher grades than beach sand deposits.
Rare earths in India, Australia and many other countries are mainly contained in monazite that is disseminated in heavy mineral sand deposits, where, typically, the rare earths grade is less than 1%.
In China, the largest source of rare earths is an iron-ore mine that contains bastnaesite and where rare earths are produced as a by-product.
Blench highlights that, when rare earths are contained in low-grade sand deposits, it is more difficult and more expensive to recover them than it is to recover them from a high-grade, hard-rock deposit like Steenkampskraal.
A bankable feasibility study (BFS) on the Steenkampskraal rare earths mine will be completed in the next 6 to 12 months.
“We have to finish the detailed engineering design of the processing plant. When the BFS has been completed, we will know what the capital budget will be. We currently estimate that the capital expenditure will be around R500-million,” Blench says.
“When we have finished the BFS, we will raise the finance to build the mine, the processing plant and the infrastructure. Construction is estimated to take about 12 months to complete.”
Blench notes that the mine’s estimated total cost to produce mixed rare-earth carbonate, which includes mining, beneficiation and chemical processing, but not the separation of the individual oxides, will be about $3.00/kg, which could be the lowest in the world.
“Thanks to our very high grade resource, we will have low operating costs. To produce 1 t of rare earths, we need to mine about 10 t of ore; most other rare earths projects have to process between 50 t and 100 t of ore to produce 1 t of rare earths, because of the low grades of those resources,” he says.
The current design has been developed to make optimum use of the existing underground infrastructure.
“Steenkampskraal is a former producing mine, with [mining major] Anglo American having mined it for ten years in the 1950s and 1960s. A shaft, developed stopes, ore blocks, underground stockpiles of ore and much of the infrastructure are already in place. Our mine plan will make the most of the existing infrastructure, which will save us about 80% of mine construction costs,” Blench points out.
He adds that the company only has to invest the remaining 20% of the required capital for the underground mining operations to start.
Steenkampskraal technical manager Witker Zimba explains that the mine design is based on conventional stoping techniques, tramming ore to the bottom of the incline shaft and hoisting the ore up the incline shaft.
With a target production rate of 2 700 t/y of mixed rare-earth oxides, about 30 000 t/y of ore will be mined and processed, after allowing for ore dilution during the mining process.
“The high grade and the small tonnage mean that mining costs will be relatively low. At this rate of production, the mine life, based on the presently known resource, will be about 25 years,” he notes.
Zimba further says the processing route involves the use of gravity separation and flotation to produce a high-purity concentrate that will contain about 90% monazite.
“A concentrate that contains copper, gold and silver will be produced as a by-product during this phase. The monazite concentrate will be chemically cleaned to remove residual apatite and sulphide contamination, after which it will be treated with caustic soda to render the rare-earth elements soluble in a dilute acid solution,” he states.
He further explains that the cerium will be removed from the mixed rare-earth salts at Steenkampskraal and refined for sale in South Africa. The cerium-depleted mixed rare-earth carbonate will be sold to companies that separate the individual rare-earth oxides.
There are 17 rare-earth elements that vary in scarcity and in their applications. “Their present relevance and importance are related mainly to their use in technologies that reduce carbon emissions and that combat global warming and climate change,” Zimba says.
Rare earths are used to make strong permanent magnets, which, in turn, are used in the electric motors that provide power for appliances, robots and electric vehicles (EVs).
“The most important application now is for EVs. The global production and sale of EVs are growing rapidly and they have electric motors that use rare earths magnets; this is increasing the demand for rare earths,” Blench notes. The increasing demand for rare earths indicates that there is an immediate demand for the mine’s production,” he says.
He points out that renewable energy is another key rare earths application, as the magnets used in wind turbines are also made of rare-earth elements. Neodymium magnets, for example, are used in industries such as electrical motor manufacture, medical science and renewable energy, which rely on high-strength neodymium magnets, Blench adds.
“Life as we know it would come to a grinding halt without rare earths,” he declares.
With the quality and grade of the feed material being so high, it is believed that Steenkampskraal has the potential to be one of the lowest-cost producers of rare earths and thorium in the world.
As part of its thorium strategy, the company plans to supply thorium oxide to Thor Medical for the production of isotopes.
Thorium is the only natural source of medical isotopes used in targeted alpha therapy (TAT), a treatment for several types of cancer.
Thor Medical is a company in Norway that is developing TAT treatments for cancer.
Steenkampskraal, together with thorium research company Thor Energy, in Norway, also completed a five-year qualification programme in April 2018 for thorium as a nuclear fuel, focusing on the commercialisation of thorium as a fuel supplement in conventional nuclear reactors.
Thor Energy is developing a nuclear fuel technology based on thorium as an alternative to uranium.
“China, India and Turkey have declared thorium part of their national power policy,” Blench notes.
Thorium fuel can use either uranium or plutonium as the fissile driver material. It is also environmentally safer and extremely difficult to use to make a nuclear weapon.
“The thorium fuel cycle is cleaner than that of uranium. In contrast, uranium produces plutonium and minor actinides in its waste, and plutonium can be used to manufacture a nuclear weapon. These minor actinides remain radioactive for thousands of years. The thorium fuel cycle produces no plutonium and hardly any minor actinides,” he explains.
Waste from the thorium fuel cycle contains mainly fission products that lose most of their radioactivity in a relatively short time, thereby substantially reducing the problems associated with the management and storage of nuclear waste, Blench adds.
“We see significant potential for thorium as a safe supplement for uranium as a nuclear fuel.”
Further, the Colorado School of Mines, in the US, published a report – ‘Thorium: Does Crustal Abundance Lead to Economic Availability?’ – in October 2014. The report includes studies of where the thorium would be sourced and states that the Steenkampskraal mine will be the lowest-cost producer of thorium in the world, with an estimated production cost of $3.56/kg.
“Once the mine is in production, we will be able to increase output in a relatively short time to meet this demand,” he says.