Business
Mkango Resources is exploring the REE deposit in Malawi.
REEs are associated with thorium, which is seen as a more
effective and safer alternative to uranium. 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 produces no plutonium and
hardly any minor actinides. Thorium isotopes are also used in the
treatment of cancer.
Reporting
Most Western hemisphere and African deposits are defined
in terms of resources and reserves, based on mineral reporting
codes, determined either by the country in which the deposited
is located, or the stock exchange where the company is listed.
These are usually benchmarked against deposits in the US. This
is due to the fact that the Mountain Pass carbonatite bastnaesite
dominated the world supply up to the late 1990s. The mine was
temporarily closed due to environmental and safety concerns and
was only periodically operated until 2015. The report should be
compiled by a competent person.
Where is the real value?
The actual REE ratios should be carefully considered when
looking at the value of a REE deposit. A developer may indicate
a high ratio of the generally more valuable HREO to LREO
compared with LREO-enriched deposits. These apparently high
ratios may, however, be largely due to yttrium. Yttrium may
dominate a particular mix of HREO, although its value generally
ranks below that of Pr, Nd, Eu, Tb, Dy, Tm, Yb, and Lu. Further
consideration is that the mining, as well as separating REO from
a higher grade LREO deposit, may be a more cost-effective
resource of HREO than a low-grade HREO-enriched deposit.
Given that current and projected consumptions of rare earths
are between 120 000 and 200 000 tons, it is clear that only
a few operations will be viable without flooding the world’s
market and impacting price levels. Other factors that have
been putting a damper on the development of African REE
projects are a lack of funding, the remoteness of the deposit,
and lack of infrastructure to move the ore from mine to port.
36 AFRICAN MINING MARCH - APRIL 2019
Finally, a significant number of the projects have been hampered
by intervention by the governments of the host country and
protracted legal actions and sited environmental issues.
Processing
Due to the extremely complex nature of REE deposits, each
deposit will have unique processing challenges, mostly related
to the mineralogy. Monazite encompasses Ce, La, Nd, Sm, and
Gd-dominant varieties. Churchite (hydrated yttrium phosphate)
encompasses Nd, Dy, and Er-rich varieties. The size and density
of REE phases will provide guidance relevant to physical
beneficiation and the understanding of the behaviour of possible
radio-nuclides.
The processing of REE is solvent extraction, again guided by the
dominant mineral composition. This ranges from atmospheric
leaching with mildly acidic conditions, to extremely aggressive
conditions. Cognisance should also be taken of any potential
by-products that can be produced, such as zircon, and how the
processing will affect the quality of by-products.
The processing component of REE is also the most cost-intensive
part of the operation. The cost of processing REE is generally
opaque and subject to strict confidentiality clauses. The different
settings and mineralogy will also have an impact, but it can be
estimated that the processing cost can be as much as the combined
cost of mining, transport, and concentration.
Rainbow Rare Earths
The only REE producing mine in Africa at the time of writing
is operated by Rainbow Rare Earths, a UK-based company.
Martin Eales, CEO of Rainbow Rare Earths, says that the fast
development of the mine, from the mining licence being granted in
2015 to delivering the first off-take material in the fourth quarter
of 2017, is due to the fact that the deposit, on surface, is capable of
free dig, with high grade, allowing them to mine a smaller volume
of material. “The mine does not perform any beneficiation of the
ore and sell a simple product that is not separated,” he says. This,
according to Eales, resulted in a low capex requirement to develop
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