Rare Earth Elements

Bastnaesite - (Ce,La,Y)CO3F- ore from Mountain Pass Mine, California. 
Source: International Business Times - Reuters Photo / David Becker

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Rare-Earth Terminology – A Refresher on the Basics
BY GARETH HATCH
December 13, 2012 
I came across a couple of online articles this week, which make reference to some pretty basic terminology with respect to the rare earths. Unfortunately these articles got much of it wrong, propagating inaccuracies that are particularly egregious when they keep appearing within various natural-resource media channels. I’m therefore going to take a little time here to address some of the key errors that keep cropping up.
First, let’s tackle one of my pet peeves. The term ‘rare-earth mineral’ is NOT synonymous with the terms ‘rare-earth elements’ or ‘rare-earth metals’. The International Mineralogical Association defines a mineral as “an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes” [1]. By this definition the element gold, for example, would be considered a mineral; however the rare earths are never found in elemental form and so in their case, the term ‘mineral’ is never synonymous with ‘element’.
Rare-earth elements (REEs) can be found in many different minerals. Only when the occurrence of such REEs is in significant quantities, or the chemical formula for a particular mineral requires the presence of one or more REEs, does the compound become a rare-earth (or rare-earth-bearing) mineral.
As for what constitutes a rare-earth element or metal; sticking with the definition formulated by the International Union of Pure and Applied Chemistry (IUPAC) will generally keep you out of trouble. IUPAC defines the rare-earth metals as the 15 lanthanoid elements (with atomic numbers of 57 through to 71) in addition to scandium (Sc) and yttrium (Y) [2]. The lanthanoid promethium (Pm) is radioactive, with no stable isotopes; it is thus present in the Earth’s crust in vanishingly small quantities and does not occur with the other REEs. Sc exhibits some properties that are similar to other REEs, but is seldom found in the same minerals as them. It does not selectively combine with the common ore-forming anions and thus it is generally (though not exclusively) confined to trace occurrences [3].
REEs are difficult to separate from one another once they have been liberated from REE-bearing minerals. At the atomic level, the lanthanoid elements have a similar outer electronic structure, with this structure shielding the so-called 4f electrons within the atom. The presence and incremental filling of these electron orbitals are key characteristics of the lanthanoids. This unique structure leads to REE ions that are very similar in size to each other. It is this similarity in ionic radii across the group, not the adjacency of their atomic numbers, which gives rise to the similar chemical properties associated with each of the REEs. This makes them difficult to separate, even with the use of intensive processes such as solvent extraction (SX).
Now we come to one of the most contentious issues with respect to rare earths, namely the definitions used to describe the specific sub-groups of REEs known as light (LREE), medium (MREE) and heavy REEs (HREEs). I freely admit that in the past year or so, I have become less forgiving of the inconsistencies that we see in the industry with respect to the use of these terms. It’s time “we” got our act together on this. One of the articles that triggered my own piece today is particularly egregious in getting this whole topic wrong.
Let’s start with a differentiation with which all chemists and geologists would likely agree, even if the non-techies in the industry don’t, namely the separation of the REEs into two groups by virtue of electronic structure. On this basis alone, the LREEs would be those that have no paired 4f electrons, specifically lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), Pm, samarium (Sm), europium (Eu) and gadolinium (Gd). This leaves the HREEs as terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Th), ytterbium (Yb) and lutetium (Lu). Because the ionic radius of Y is very similar to that of the HREE Dy, Y is generally included as a HREE, despite not having any 4f electrons, paired or otherwise. In contrast, the ionic radius of Sc is much smaller than any of the other REEs and is therefore generally NOT classified as being either a LREE or HREE.
There are many in the industry that classify Eu and Gd as HREEs, but there really is no sound basis for doing so, unless you consider the inflation of a project’s HREE numbers as being a “sound basis”…
So now let’s turn our attention to the so-called MREEs. Of the relatively few sources in the industry that acknowledge the existence of this group, most of them get the composition of it wrong as well as its origin. The MREEs specifically refer to Sm, Eu and Gd, and the term arose from the metallurgists, process chemists and others who calculate and design the process flow sheets required to complete the separation of REEs from each other. This definition of the MREEs is the same one that the Chinese authorities use, by the way, when talking about the export quotas allocated to light rare earths, and to medium/heavy rare earths.
The MREE or SEG group as it is also known, arises within the early stages of SX, the main commercial process used to separate and to purify REEs, because of the absence of Pm from the feedstocks used. As we saw earlier, although Pm is a LREE, it does not occur with the other REEs, and so the process chemists take advantage of this “blip” in the sequence of REEs, caused by the resulting “gap” between Nd and Sm, during the separation process.
 The MREE group therefore arises for process engineering reasons only and does not require any new definitions, or changes to existing ones. The purists and certain laypeople can argue that these elements should strictly be defined as LREEs; such individuals should simply see the MREEs as a subset of the LREEs and worry themselves no more. I prefer to use all three terms – LREEs, MREEs and HREEs – and have been doing so exclusively for the past 18 months as I get more and more into the processing side of the rare-earth industry. Either way, you now know the origin of the term, and the three REEs to which it correctly refers. Either way, you also now know that Eu and Gd are really NOT HREEs.
Finally, the last term that I use quite a lot is critical REEs (CREEs), in reference to the five REEs that are of critical importance to future demand for sustainable energy sources – specifically Nd, Eu, Tb, Dy and Y.
As I always tell people – just make sure that you understand exactly which definitions a particular company is using, when looking at reported data which use one or more of the group names described above. In the meantime, let’s hope that certain of my fellow commentators on the rare-earth sector start to get the hang of the basic terminology for these materials…
References
1. E. H. Nickel, The Canadian Mineralogist, 1995, Vol. 33, pp. 689-690.
2. N. G. Connelly, T. Damhus, R. M. Hartshorn and A. T. Hutton, 2005, Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005, RSC Publishing, Cambridge, p. 366.
3. J. B. Hedrick, 2000, Minerals Yearbook: Volume I – Metals and Minerals, US Geological Survey, Reston, p62.1

Rare earth elements and their compounds have many uses but the quantities consumed are relatively small in comparison to other elements. About 15000 tonnes/year of the rare earths are consumed as catalysts and in the production of glasses. From the perspective of value, however, applications in phosphors and magnets are more important.



Rare Earth Oxides (REO) used as tracers to determine which parts of a watershed are eroding. Clockwise from top centre: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium.                        Source: United States Department of Agriculture

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RankCountryWorld Mine Production, By Country (Metric tons of rare earth oxide equivalent)
1China125,000125000
2India2,7002700
3Brazil550550
4Malaysia380380
Year of Estimate: 2008
China sets up rare earth industry association (Resource Investing News, 19 April 2012) 
China recently announced that it has set up a rare earth association to speed up the unification of the diverse industry, which has drawn criticism from what many overseas trade partners are calling unfair export quotas.

According to the state-run Xinhua news agency, the association will consist of 155 members across the country, and will report to the Ministry of Industry and Information Technology, which is currently responsible for regulating rare earth production.
“Shake up the industry”
Su Bo, an industry vice minister, announced that the move was made because Beijing wants to “shake up the industry” by phasing out smaller-scale smelters, giving large players a greater stake in the supply of rare earth metals and in turn boosting environmental protection.
“China will continue to clean up the rare earth industry, expand rare earth environmental controls, strengthen environmental checks, and implement stricter rare earth environmental policies,” said Bo.
Less than a month ago, the already tense US-China relationship took a new turn as the US, EU, and Japan moved in on the World Trade Organization (WTO) to challenge China’s restrictive rare earth export policies.
Some speculators argue that China’s goal is to create the ultimate monopoly by driving up export costs to the point that technology manufacturers are forced to relocate their facilities to the People’s Republic.
It was also announced that Gan Yong, the President of the Chinese Society of Rare Earths, will be president of the new association. He claimed that the body will help to “form a reasonable price mechanism” at a time when China is being accused of deliberately forcing up prices by minimizing exports.
Molycorp updates resource estimate
Meanwhile, Molycorp Inc. (NYSE:MCP), one of the only non-Chinese producers of rare earth, has raised its estimates of reserves contained at its California mine.
According to a company press release, a new independent study has confirmed that its Mountain Pass mine contains 36 percent more probable or proven reserves than originally estimated. It now estimates reserves at 2.94 billion pounds of contained rare earth oxide equivalent, compared with a previous estimate of 2.24 billion pounds.
The updated analysis is influential in that it means that Molycorp’s total proven and probable reserves now add up to approximately eleven times the current global demand of 120,000 tonnes a year, most of which is supplied by Chinese producers. The company has stated that it expects output at the mine to reach its phase one annual rate target of 19,050 tonnes by the end of the third quarter of 2012.
From a market competitiveness perspective, the updated estimate comes at an ideal time for Molycorp as the miner’s closest competitor outside of China, Australia’s Lynas Corporation Ltd. (ASX:LYC), is facing numerous permitting delays at its processing facility in Malaysia.
Market price update
It has been an active week for rare earth prices as lanthanum/cerium mischmetal prices rose on the back of an improvement in downstream demand and a rise in raw material prices.
Market sources confirmed that prices for lanthanum/cerium mischmetal (La 35 percent, Ce 65 percent) moved up to trade around RMB85,000/tonne in comparison to RMB80,000/tonne a week ago.
An unnamed source at a Chinese-based producer was quoted in the media as saying that “[m]ore downstream consumers have been tending to buy mischmetal recently and sales for the material have been running.”
He added that an increase in lanthanum/cerium chloride prices has also contributed to the rise in lanthanum/cerium mischmetal prices. Prices for lanthanum/cerium chloride (La 35 percent, Ce 65 percent) are currently holding at RMB22,000/tonne, up from RMB18,000 to 20,000/tonne a week ago.
Dysprosium oxide prices saw no change last week, closing the trading at RMB4,300 to RMB4,600 per kilogram. Samarium prices also remained flat throughout last week at RMB270,000/tonne, while gadolinium maintained its pricing at RMB178,000 per metric tonne.
Junior mining news
Quantum Rare Earth Developments Corp. (TSXV:QRE) CEO Peter Dickie noted in an interview that based on an updated resource estimate, Quantum’s Elk Creek, Nebraska niobium project could cut US dependence on imports of the strategic material.
He also said that the project contains one of North America’s largest undeveloped niobium deposits in terms of grade and tonnage, and is the only primary niobium deposit under development in the US.
The updated estimate shows a resource containing over 129,000 tonnes of niobium (Nb2O5) in the indicated category, and over 524,000 tonnes of niobium (Nb2O5) in the inferred category, with the deposit open in three directions.
Great Western Minerals Group Ltd. (TSXV:GWG) announced that it is on track for its strategy of becoming a fully-integrated rare earth producer and processor.
The rare earth focused company has several operational targets this year, including the refurbishment of the mine shaft at the Steenkampskraal mine in South Africa and the completion of the NI 43-101 report for the mine by mid-May.
The company recently unveiled assay results from the first batch of samples taken as part of the phase one program at Steenkampskraal. Within the underground channel sampling results, assays ranged from 15.9 percent total rare earth oxide (TREO) to 40.12 percent TREO with an average of 23.75 percent TREO.
Drill core assays ranged from 0.18 percent TREO to 31.07 percent TREO, with an average grade of 13.83 percent TREO. Surface tailings results from the first batch of 54 assays ranged from 3.85 percent TREO to 12.01 percent TREO with an average of 7.27 percent TREO.
The remaining results from the phase one program will continue to be released over the next few weeks.

Dominating the World: China and the Rare Earth Industry

Rare Earth Prices

There is a significant variance in the relative market value for selected rare earth oxides. The price of rare earths also depends on the purity level, which is largely set by the specifications for each application.
In 2001, when rare earth prices fell to low levels, the major producers ceased publication of prices and have not resumed since then. The industry today, is reliant on the prices given by the Chinese Rare Earth Information Centre, Mineral Price Watch, Metal Pages and others.

Historical prices

The weighted average price of rare earths remained relatively stable throughout the mid 1990’s in the range of US$ 9-11/kg REO, falling to US$ 5-6/kg REO in 2001/02. The high demand for magnets and phosphors has lifted the estimated 2006 average price for rare earths to US$ 8-9/kg REO. An equivalent weighted average price for October 2007 rose to US$11.75/kg - US$12.50/kg REO.

In December 2009 the price remained unchanged for europium oxide (99%, bulk FOB China), at $490/kg. The price for lanthanum oxide (99% bulk FOB China) edged up to $5.80/kg from $5.20/kg.

The price for neodymium oxide (99% bulk, FOB China), a necessary component in new magnet technology and used in computer hard drives, currently stands at $19.5/kg compared to $30.5/kg in December 2007. In 2008 the price was $14.5/kg showing that there has been some recovery over the last couple of months. The price of praseodymium oxide (99%, bulk FOB China) stands at $19/kg, down from $28/kg two years ago, but up from $14.5/kg in December 2008. Rare earth mineral prices do not follow the same trajectory, but are driven by their individual end-use markets. Chinese domestic prices for cerium-oxide (CeO2>99%), widely used in glass, ceramics and catalyst manufacturing, which were around $1.76/kg in November 2007, have gained as much as 50% to $2.64/kg in December 2009. (Rare Earths waiting for rebound, Industrial Minerals Division of Metal Bulletin, 10 December 2009).


It has been predicted that by 2014, global demand for rare earths will reach 200,000 tonnes a year and that by 2015 China will be a net importer.

The Economic Geology of Rare Earth Deposits

The rare earths are a relatively abundant group of 17 elements composed of the lanthanides plus scandium and yttrium.

The elements range in crustal abundance from cerium, the 25th most abundant element of the 78 common elements in the Earth's crust, at an estimated 46 parts per million, to europium and erbium, the least abundant rare-earth elements, at about 0.5 and 0.4 parts per million respectively.

Rare earth elements (REE) are widely distributed in low concentrations (10 to 300 ppm) in shales, granites, alkaline rocks and carbonatites.


From the discovery of REE (during the period 1794–1907) through the mid-1950s, a few of the REE were produced in modest amounts from monazite-bearing placers and veins, from pegmatites and carbonatites (carbonatites are intrusive igneous rocks rich in carbonate minerals), and as minor by-products of uranium and niobium extraction. Monazite, the single most common REE mineral, generally contains elevated levels of thorium. Although thorium itself is only weakly radioactive, it is accompanied by highly radioactive intermediate daughter products, particularly radium, that can accumulate during processing. Concern about radioactivity hazards has now largely eliminated monazite as a significant source of REE and focused attention on those few deposits where the REE occur in other, low-Th minerals, particularly bastnaesite.

In 1949, a carbonatite intrusion with extraordinary contents of light REE (8 to 12% rare earth oxides) was discovered at Mountain Pass, in the upper Mojave Desert, California. The REE at Mountain Pass are hosted chiefly by bastnaesite, (Ce, La, Nd…) CO3F, and related minerals. By 1966, this single, world-class deposit (now owned and operated by Molycorp Minerals LLC) had become the paramount source of REE. Early development was supported largely by the sudden demand for europium created by the commercialization of colour television. Mountain Pass, with an average grade of 9.3% and reserves of 20 million metric tons (Mt) REO (at 5% cut-off), remains the only large ore deposit mined solely for its REE content.

Molycorp Mountain Pass rare earth pit in California's Mojave Desert

Chinese REE production comes chiefly from two sources.

The most important is the giant polymetallic Bayan Obo iron-niobium-REE deposit, Inner Mongolia. Bayan Obo is the world's largest known REE ore deposit and represents 70% of the world's REE resources. Ongoing statistics shows total reserves of 89 million tonnes of RE2O3 in China.
The principal REE minerals are bastnaesite [(Ce,La,Nd)(CO3)F] and monazite [(Ce,La,Nd)PO4], whereas magnetite and hematite are the dominant iron-ore minerals.
This deposit has geological affinities both to carbonatite REE deposits and to hydrothermal iron-oxide (Fe-Cu-Au-REE) deposits, such as Olympic Dam, Australia, and Kiruna, Sweden.
The ore body at Bayan Obo is mainly an iron resource with reserves of 1.46 billion tonnes Fe. The associated rare earths resource, which is produced as a by-product of the iron ore mining and mineral concentration operations, has been estimated at 57.4 million tonnes REO. Grades at Bayan Obo vary from 3% to 6% REO. The total reserves of niobium are estimated at 1 million metric tons with an average grade of 0.13 Nb wt%.

The location of the Bayan Obo deposit and its geological setting.

The second major source of Chinese REE is ion-adsorption ores in lateritic weathering crusts and clays developed on granitic and syenitic rocks in tropical southern China.
These oxide ores are advantageous in their relatively high proportions of heavy rare earth elements (HREE) and, especially, in the ease with which they can be mined and the REE extracted. (U. S. Geological Survey Fact Sheet 087-02 - Rare Earth Elements—Critical Resources for High Technology: http://pubs.usgs.gov/fs/2002/fs087-02/).

Ion-absorbed-type rare earth minerals found in China – the white, gray, red, yellow loose sand clay, called ion-absorbed-type rare earth raw ore, also called weathering crust of rare earth ore leaching plot..

Worldwide about 200 rare earth minerals are distributed in a wide variety of mineral classes, such as halides, carbonates, oxides, phosphates, silicates, etc. Light rare earth elements (LREE i.e. lanthanum, cerium, neodymium, praseodymium and samaruim) tend to concentrate in carbonates and phosphates.

On the other hand, heavy rare earth elements (HREE) and Y are abundant in oxides and in some phosphates. 

One probable hypothesis for ore genesis is that the deposits might be formed by hydrothermal replacement of carbonate rocks of sedimentary origin.

The hydrothermal fluid may be derived from an alkaline–carbonatite intrusive series. Following Bayan Obo, more than 550 carbonatite/alkaline complex rocks constitute the majority of the world REE resources.

The distribution is restricted to interior and marginal regions of continents, especially Precambrian cratons and shields, or related to large-scale rift structures.

Sedimentary deposits of REE are placer- and conglomerate-types. The major potential countries are Australia, India, Brazil, and Malaysia. Weathered residual deposits, like the ion adsorption clay without radioactive elements in southern China, have been formed under tropical and sub-tropical climates.

Weathering processes concentrate REE in a particular clay mineral-layer in the weathered crusts whose source were originally REE-rich rocks like granite and carbonatite. (Yasuo Kanazawa and Masaharu Kamitani: Rare earth minerals and resources in the world, Elsevier B.V., 2005).

One of the more important deposits presently being developed worldwide is
the Mt Weld carbonatite deposit in Australia, known as the ‘Central Lanthanide Deposit’ (CLD) is, according to Lynas Corporation Ltd, the world’s richest rare earth ore body, easily capable of supplying up to 20% of the global market for 30 years. Indicated and Inferred Resources total 37.7 million tonnes of ore. In 2011Total Mt Weld estimate increased to 17,490kt at 8 .1%– a new contained REO of 1,416kt 
An initial mining campaign was successfully completed in June 2008. The campaign mined 773,300 tonnes of ore with an average grade of 15.4% Rare Earth Oxides (REO). The ore is stockpiled on-site and is sufficient for the first two years of the downstream processing operation.



The Kangunkunde Carbonatite Complex deposit in Malawi has an inferred resource of 107,000 tonnes of rare earths oxide (REO) at an average grade of 4.24% REO in 2.53 million tonnes of mineralization using a cut-off grade of 3.5% REO.

The mineralization commences on the surface and the deposit remains open at depth. The relatively low cut-off grade is justified by the demonstrated amenability of the ore to low cost gravity separation to produce a high-grade concentrate.

The rare earth elements are mainly concentrated in the monazite mineralization and the distribution is as follows: La2O3 - 29.8%, CeO2 - 49.7%, Pr6O11 - 4.7%, Nd2O3 - 14.0%, Sm2O3 - 1.05%, Eu2O3 - 0.19%, Gd2O3 - 0.36%, Tb4O7 - 0.07%, Dy2O3 - 0.08%, Others - 0.04%. The monazite content of the ore averages more than 5%.

The deposit has low thorium oxide levels for a rare earths resource and samples averaged 11 ppm thorium oxide per percentage of REO content. (Lynas Corporation Ltd, http://www.lynascorp.com).

Occurrences of thorium, yttrium and rare earth elements in Namibia are known to be associated with carbonatites and granites and pegmatites of Namibian and Mesozoic age. Placer deposits of these minerals have formed mainly in Tertiary to Recent times in the marine environment.

Thorium, yttrium and rare earth element mineralization associated with carbonatites

The Lofdal-Bergville carbonatite dykes and plugs.

The Lofdal-Bergville carbonatites are located 30 km west of Khorixas in Damaraland on the farms Lofdal 491 and Bergville 490, where syenite, porphyry, tinguaite, lamprophyre, fenite and carbonatite dykes and plugs have intruded Huab Complex gneiss.

The carbonatites are highly radiogenic and contain xenotime, bastnaesite and thorite. Other alkaline intrusives occur south of Lofdal 491 on the farm Oas 486. The Oas syenite intruded rocks of the Nosib Group.
atites on Lofdal-Bergville were investigated in 1982, and thorium and yttrium values from 0.17% to 14.4% ThO2 and 0.05% to 0.63% yttrium were obtained. In addition to the radiogenic minerals and calcite, the carbonatites contain limonite, hematite, magnetite, zircon, fluorite and apatite.
A sample of a carbonatite dyke assayed as follows: lanthanum 1.5%, cerium 0.87% and neodymium 0.74%.


Namibia Rare Earths files maiden Lofdal resource, confirms HREE
By: Henry Lazenby
Published: 26th September 2012
TORONTO (miningweekly.com) –

Namibia Rare Earths(NRE) had filed a maiden resource for its Lofdal rare earths elements project, confirming the presence of high levels of heavy rare-earth enrichment (HREE) in certain areas of the project.
The National Instrument 43-101-compliant resource estimate, covering Area 4 of the project located in the north-west of Namibia, pointed to “exceptional”
levels of HREE of between 75% and 93% HREE, depending on the cut-off grade, with corresponding total rare earth oxide grades (TREO) ranging from
0.27% to 1.26%.
What distinguishes the project from many other juniors that have entered the market in response to China’s reduction of exports over the past four years
– the country produces over 95% of the world’s rareearth’s supply – is its concentration of what are called heavy rare earths. “Given current rare-earth prices, over 90% of the value in this deposit lies in the four critical heavy rare
earths – europium, terbium, dysprosium and yttrium – with less than 2% of the value relating to lanthanum and cerium, the most common light rare earths,” NRE president Don Burton said in a prepared
statement.
Mining consultancy The MSA Group of South Africa prepared the estimate had identified the presence of an indicated resource, at a 0.3% TREO cut-off, of 900 000 t at 0.62% TREO, with 86% HREE, and an inferred resource of 750 000 t grading 0.56% TREO, with 85% HREE. The resource was drilled to a depth of 150 m and remained open at depth and along strike. At a low-grade cut-off of 0.1% TREO, the resource estimate provided for 2.88-million tons grading 0.32% TREO, with 76% HREE in the indicated category, and 3.28-million tons grading 0.27% TREO, with 75% HREE in the inferred category.
The company said it was still studying the most appropriate cut-off grade. NRE said a metallurgical study programme was also currently underway with Commodas Ultrasort, in Germany, and South African metallurgical specialist Mintek, to demonstrate the viability of extracting the rare earths from Area 4.
Burton also noted that subject to favourable outcomes on the metallurgy studies, the entire mineral resource at Area 4 could be upgraded from indicated and inferred to measured and indicated categories without any further drilling. However, there still remained substantial upside potential to increase the resource through further exploration of the 200 km2 Lofdal carbonatite complex.
The Halifax, Nova Scotia-based company debuted on the TSX in April, after it raised C$25-million in an initial public offering, in preparation for undertaking the resource estimate.

The Eureka carbonatite dykes

Monazite-bearing carbonatite dykes on the farm Eureka 99, located approximately 38 km west of Usakos, and about 2 km north of the Usakos-Swakopmund road, contain rare earth mineralization.

With the exception of a single occurrence of a sovite dyke, all the carbonatite dykes at Eureka are beforsitic in composition, but have varying concentrations of monazite.

The monazite-rich beforsites are characterised by rare earth oxide concentrations that range between 33% and 40%.

Drilling established proven reserves of 30 000 t of ore to a depth of 20 m, containing 1 900 t of rare earth elements.

The Kalkfeld Alkaline Complex

Thorium, yttrium and rare earth element mineralization is known to be associated with four carbonatite complexes in the Otjiwarongo and Grootfontein Districts. These complexes belong to a northeast-trending line of over 20 intra-plate-type, subvolcanic, ring complexes of the Damaraland Alkaline Province.

Within these complexes, thorium, yttrium and rare earth element mineralization is associated with late-stage plugs and dykes of mainly beforsitic composition, or with iron-rich, late-stage metasomatites. Three of the carbonatite complexes also carry disseminated pyrochlore.

The Kalkfeld complex is situated on the farm Eisenberg 78, about 11 km northwest of Kalkfeld, and measures about 5 km in diameter. The complex consists of confocal rings of granite, syenite, foyaite and carbonatite.

A plug of massive iron ore occupies the central area of the complex. The carbonatites and the iron ore show an enrichment in lanthanum (500 to 5 000 g/t), cerium (2 000 to 8 000 g/t) and neodymium (1 000 to 2 500 g/t). 


The Ondumakorume Complex

The Ondumakorume Complex forms a prominent hill on the farm Etaneno 44, about 10 km northeast of Kalkfeld. In addition to syenite, nepheline syenite, volcanic breccia and iron ore, micaceous sovite, grey sovite and beforsite are the main types of carbonatite. Rare earth minerals such as monazite, ancylite, cerianite and carbocerianite occur within beforsite with whole rock concentrations of up to 9 000 g/t cerium.


The Osongombe Complex

Osongombe is the smallest of the Damaraland carbonatite complexes and is situated about 12 km southwest of Kalkfeld on the farms Osongombe 80, Sud Osongombe 83 and Okarume 82.

The diatreme consists mainly of volcanic breccia and beforsite together with iron ore. The beforsite occupies the central area of the complex and is composed of manganiferous ankerite, apatite-rich aggregates magnetite-siderite, quartz and accessory, finely disseminated, yellowish octahedra of pyrochlore.

The Okorusu Alkaline Complex

The Okorusu Alkaline Complex is situated 45 km north-northeast of Otjiwarongo. The complex is composed of a series of alkaline rocks including hortonolite monzonite, various syenites, foyaite, urtite, tinguaite, nephelinite and carbonatite.

The southern portion of the complex is characterised by the presence of various metasomatites including aegirine fenite, limonitic iron ore and numerous ore bodies of fluorite that were formed by replacement of dolomitic marbles.

The carbonatites at Okorusu occur as pluglike bodies and dykes that have variously intruded aegirine fenite, rocks of the metasomatic aureole and the central area of the complex.

On the farm Brandenberg 87 a number of beforsitic carbonatite dykes and carbonate fluorite- bearing metasomatites carry appreciable amounts of rare earth element mineralization of mainly pale yellowish-brown synchisite, green monazite and yttrio-fluorite. Some of the dykes are up to 20 m wide and can be followed for up to 300 m along strike.

Synchisite occurs as fibrous needle-shaped or as plate-like crystals and is mainly associated with carbonate-quartz-fluorite-barite-thorite-monazite and xenotime-bearing assemblages.

The total rare earth oxide content in the siliceous rocks varies from 1.5% to 7%. The thorium and yttrium values of these rocks range from 0.4% to 3.5% thorium and from 0.2% to 1.01% yttrium.


The Agate Mountain Carbonatite Complex

About 8 km northeast of False Cape Fria, on the north-western coast of Namibia, a carbonatite complex has intruded Karoo Sequence volcanics. Bastnaesite is associated with late-stage beforsitic (Mg-rich) carbonatite and occurs in irregularly distributed patches.

Thorium, yttrium and rare earth element occurrences associated with granites and pegmatites

Some of the post-tectonic biotite granites of late Pan African age and, in particular, Pan African pegmatites, are known to contain accessory monazite, gadolinite, allanite, thorianite and yttrio-fluorite.

Wlotzkasbaken allanite occurrence

Phenocrysts of allanite, up to 60 mm in length, occur in a coarse-grained Pan African granite northeast of Wlotzkasbaken, 30 km north of Swakopmund. The allanite crystals are extremely well disseminated and the granite has not been investigated for other rare eartk minerals or sampled for total rare earth content.

The Brandberg Alkaline Complex

Zoned allanite occurs in potassium metasomatised biotite granite of the Brandberg Alkaline Complex, whereas chevkinite, monazite and fluorite are commonly associated with potash-altered, biotite granite.
Peralkaline granites and sodium-rich fenites that are associated with the Amis complex, located on the southwestern periphery of the Brandberg complex, contain anomalous whole rock yttrium (up to 2 000 g/t) and thorium concentrations (up to 700 g/t).

Fenitised peralkaline granites and agpaitic pegmatites of the Amis complex contain Y-fluorite, monazite, xenotime, bastnaesite and fergusonite. The Amis Complex represents a late intrusive phase associated with the Brandberg anorogenic granite intrusion.

It consists of peralkaline, arfvedsonite-bearing granitic and pegmatitic dikes and sills and is characterized by locally extreme enrichments in REE and rare metals with high charge-ionic radius ratios, such as Zr and Nb.

The highest concentrations (e.g., 1.7 wt % Zr, 0.3 wt % Nb, 0.5 wt % total REE) are found in aegirine-albite aplites that formed around arfvedsonite pegmatite cores.

Thorium, yttrium and rare earth element occurrences associated with placer deposits

Toscanini monazite occurrence

A monazite-bearing marine placer deposit was found in the Skeleton Coast Park near Toscanini. The monazite-bearing sands occur along a coastal strip some 22 km long, stretching from about 31 km south of Torra Bay to 20o 40’ south.

The extent of the deposit is outlined by a prominent radiogenic anomaly. The bedrock consists of quartz latites of the Etendeka Formation and sediments of the Toscanini Formation. The source of the monazite is unknown, but it can be speculated that it is possibly derived from Pan African granites that occur south of the deposit.

The monazite was presumably transported in a northerly direction by the Benguela current and subsequently concentrated and deposited by marine processes.

Rare earth element mineralization in South Africa occurs in heavy mineral sand deposits, in pegmatites and granites of the Namaqualand Metamorpic Complex, in carbonatites and alkaline complexes and in the fluorite-bearing rocks associated with the Bushveld Igneous Complex. 

South Africa’s known and demonstrated recoverable reserves were estimated in 1988 at 2.187 million metric tons of REO in two deposits; placer monazite at Richards Bay and rare earth bearing apatite at the Phalaborwa Complex (Van der Vyver, G P: Resources of Rare Earths in South Africa, Minerals Bureau, 1988).

These reserves, at the time, placed South Africa third in the world after China and the USA, but South Africa never developed a rare earth mining and refining industry. The other known occurrences in South Africa have not been adequately explored to be classified as demonstrated resources.
Although South Africa produced rare earth-bearing monazite concentrates at Richards Bay Minerals (RBM), production stopped before 2003 and RBM, like Ticor and Namakwa Sands, currently recovers only ilmenite, rutile and zircon.

The rare earth-bearing apatite concentrates of Phalaborwa have been investigated by MINTEK repeatedly with the view of producing rare earth oxides.

The Steenkampskraal monazite mine at Van Rynsdorp in Namaqualand, operated from 1952 to 1963, producing a monazite concentrate that was sold mostly for its thorium content rather than its rare earth content. It was the largest thorium source in the world during the years 1951 to 1963.

Richards Bay Minerals
Placer-type deposit with monazite plus thorium and consequently with a radioactive hazard problem.

Richards bay Minerals (RBM), jointly owned by Billiton and Rio Tinto, is the largest single producer of titanium in the world from heavy mineral deposits. RBM now accounts for about 25% of world output of titanium feedstocks (titania slag and rutile), 33% of world zircon output and 25% of high purity pig iron. The sand deposits contain REE-bearing monazite and the recoverable resource was estimated at 27,500 tonnes REO in 1988.

Phalaborwa Complex
Carbonatite-type deposit with a low-grade, high tonnage potential

The Phalaborwa Complex is a zoned pyroxenite-syenite-carbonatite intrusion located on four farms in Mpumalanga Province. It hosts South Africa’s largest copper mine and produces, in addition, magnetite, sulphuric acid, zirconia, uranium, precious metals, vermiculite (Rio Tinto) and phosphate (FOSKOR).

The REE occur mainly in the phosphate mineral apatite and the P2O5 content varies from 6% to 8% within the pyroxenites and the foskorite (altered magnetite-olivine-apatite carbonatite). Rio Tnto’s Palabora Mining Company has a standing contractual arrangement whereby the apatite concentrates are delivered to FOSKOR for the production of phosphate in exchange for copper concentrates from FOSKOR. The apatite concentrate contains on average 0.5% rare earth oxides. The total recoverable resource has been estimated at 2,160, 000 tonnes REO.

The europium content is in excess of 1% in the rare earth concentrates and the thorium oxide content of the rare earth concentrates is below 200 ppm. FOSKOR’s associated company, Sentrachem, conducted various investigations and tests by MINTEK on the concentrates with the view of recovering the individual rare earths.

Steenkampskraal monazite mine
Pegmatite-type deposit with low tonnage potential
The Steenkampskraal monazite deposit occurs in a sequence of highly metamorphosed crystalline gneisses of the Roodewal Suite of the Namaqualand Metamorphic Complex.
The rocks are the host in which the pegmatite ore body occurs. The monazite-bearing ore body is tabular in shape with an undulating form and a thickness varying from 30 cm to 90 cm.
Minerals present in the ore body include monazite, quartz, apatite and magnetite with small amounts of zircon, pyrite, chalcopyrite, galena and ilmenite. The monazite is the source of the rare earths. The average in situ grade is 16.74% REO, 0.8% Cu, 0.5g/t Au and 6.0g/t Ag. The estimated reserve is 20 00 tonnes REO.
Great Western Minerals Group Ltd (Canadian) has an option to explore, develop and eventually buy the total production from Rare Earth Extraction Company Ltd. The developer of the South Africa-based Steenkampskraal rare-earths project, TSX-V-listed Great Western Metals Group (GWMG) said in May 2012 it had filed a Canadian National Instrument 43-101-compliant resource report with Canadian Securities Administrators.

The report states that Steenkampskraal hosted a resource of 131 500 t of rare-earth minerals in the indicated and inferred categories, with about 37 500 t of resources located in the upper and lower tailings dams.


GWMG said it had notified its escrow agent that it had satisfied the escrow release condition of the $90-million convertible bond financing and expects the remaining $10.8-million, earmarked to satisfy interest payments, to be released to the company in due course.


In order to satisfy the escrow release condition, GWMG had to confirm that at least 20 000 t of total rare-earth oxides (TREO) including yttrium, in the sum of the measured, indicated, and inferred resource categories are present at the Steenkampskraal property using a 1% cut-off grade.


The NI 43-101 report pointed to the presence of 13 823.64 t of TREO including yttrium under the indicated resource category and 14 147.76 t under the inferred resource category.


The aspiring integrated rare-earths producer on Wednesday said it had narrowed its first-quarter loss to $3.06-million when compared with the loss of $4.86-million in the same period a year ago.
Other carbonatites and alkaline complexes with rare earth element mineralization.

Mineralized carbonatites usually contain a high concentration of the so-called light rare earth elements lanthanum, cerium, neodymium, praseodymium and samaruim. The minerals containing the rare earths occur dispersed in the calcite (Ca-rich), and, dolomite (Mg-rich) and ankerite (Fe-rich) forming the bulk of the carbonatite.

If a carbonatite or complex consists of multiple intrusions or phases, the rare earth element content tends to increase in the youngest phases. Apatite is considered to be an accessory phase of carbonatites and contains substantial rare earth elements remobilised by hydrothermal fluids.

The rare earth minerals bastnaesite, parisite and synchisite are considered to be supergene, i. e. formed at shallow depth by the action of groundwater. (Mountain Pass in California and Mt Weld in Australia, where the ore-grade mineralization occurs between 30 metres and 60 metres below the present-day surface, are examples where the supergene enriched portions of the carbonatites are of economic interest).


The Glenover Carbonatite Complex

The Glenover Carbonatite Complex, 80km north-northwest of Thabazimbi, comprises an oval shaped, poorly exposed pyroxenite and carbonatite body, 4.7 km long and 3.5 km wide. Monazite is bound in a coarse-grained sövite (Ca-rich) and magnesio-carbonatite.
Associated minerals include apatite, magnetite, phlogopite and pyrochlore. Associated secondary minerals include quartz, synchisite, fluorite, barite, monazite and columbite. The presence of synchisite could indicate supergene enrichment in rare earth mineralization of the brecciated complex, but there is no information available on the distribution of the rare earth minerals.

The Kruidfontein Complex

The Kruidfontein Complex is situated approximately 130km north-northwest of Pretoria. It has a caldera structure, along a NW-striking regional fault. The carbonatites represent the last stage of extrusive activity of the Kruidfontein Complex.

Rare earths associated with fluorite (CaF2) mineralization occur associated with the intrusive (fluorite-rich dykes and plugs) and extrusive (replacement and disseminated ore) carbonatitic rocks.

A large tabular stratiform ore body occurs in the southwestern part of the Complex, and contains an average of 30% CaF2. Fluorite occurs disseminated throughout the inner zone with concentrations not exceeding 10% CaF2. Analytical results from the inner zone show that the fluorite contains La2O3 in variable concentrations between 0.02 and 0.15 wt%.

The Pilanesberg Complex

Rare earths are found in alkaline rocks of Pilanesberg on Thabayadiotsa on the farms Houwater 54, Rhenosterspruit 59 and Saulspoort 38.

Rare earth mineralization on Houwater 54 occurs as veins in the contact zone between a tinguaite ring dyke and younger foyaite, On the farm Rhenosterspruit 59, rare earth mineralization occurs in tuff bands intercalated with lava over a distance of 2 km. On the farm Saulspoort 38, rare earth mineralization occurs as veins in a white foyaite. Yttrium and REE are concentrated in britholite ((Ce,Ca,Th,La,Nd)5(SiO4,PO4)3(OH,F) ) veins and britholite-bearing foyaite.

High grade mineralization consists of britholite containining 56.36% REO and 1.56% ThO2 and magnetite with minor amounts of allanite, apatite, calcite, strontianite, fluorite, aegirine and cheralite.

The reserves have been estimated at 13.5 Mt at 0.7% REO +ThO2, 1.2 Mt at 6.54% REO +ThO2, and 24 000t at 10% REO+ThO2.

The Vergenoeg magnetite-fluorite deposit

The Vergenoeg breccia pipe is located in Gauteng Province approximately 80 kilometers northeast of Pretoria. Vergenoeg is a fluorite-bearing massive iron oxide deposit that is genetically related to granites of the Bushveld Complex.

The deposit is a funnel-shaped breccia pipe, with a diameter of 900 m (north-northwest) to 700 m (east-northeast) on surface, which contains fluorite, apatite, ilmenite and magnetite.

Vergenoeg is a fluorite mine, despite the large volumes of magnetite and has produced fluorite since 1956. The fluorite ore body, up to a depth of 360 m has a resource estimate of 174 Mt at 28.1% CaF2. The iron resource is in the order of 195 Mt at 42% Fe.

Mining has been focused on the upper part of the pipe-shaped body (porous botryoidal hematite-goethite gossan). The gossan contains resistant minerals such as cassiterite, apatite and rare earth carbonates.

Siderite is often found with the REE minerals, normally occurring in veinlets and coarse-grained masses. REE minerals in the upper part of the pipe may have originated from remobilization of allanite from the lower part of the pipe.

Similarly remobilization might have resulted in the REE mineralization seen in the siderite veins and interstitial grains between apatite laths, including monazite.

The primary assemblage of minerals in the lower part of the Vergenoeg pipe comprises mainly of fluorite, ilmenite and fayalite (Fe2SiO4) with minor pyrrhotite, apatite and allanite.
Allanite is the most common REE-bearing mineral in the primary mineral assemblage and are intergrown with fayalite and ilmenite.

It seems that the REE potential of Vergenoeg has not been investigated systematically and no further information on the distribution and grade of the REE mineralization could be obtained.
Similarities with Phalaborwa and also with Bayan Obo, Mongolia, indicate that the Vergenoeg pegmatoid pipe could be an extreme carbonatite-associated member of the Fe-oxide Cu–Au (±REE±P) group of deposits. (Goff, B. H., Weinberg, R, Groves, D. I.; Vielreicher, N. M.; Fourie, P. J.: The giant Vergenoeg fluorite deposit in a magnetite–fluorite–fayalite REE pipe: a hydrothermally-altered carbonatite-related pegmatoid?; Mineralogy and Petrology, Volume 80, Numbers 3-4, March 2004 , pp. 173-199).
Metorex sold its 55% shareholding in Vergenoeg to its Spanish partner, Minerales y Productos Derivados S.A. (“Minersa”) in December 2009 for US$60 m. (Metorex acquired the mine in 1999 when its former owner - chemical giant Bayer - decided to sell out as part of its drive to dispose of non-core operations and concentrate on its main business - the manufacture of chemicals.
Metorex then promptly sold 30% of Vergenoeg to the Spanish chemical group Minersa, which also bought a 20% direct stake in Metorex itself, becoming one of the group's largest shareholders).
The Buffalo Fluorspar Deposit

The deposit is situated about 75 km north of Vergenoeg near Mookgopong (formerly Naboomspruit) in Limpopo Province and contains fluorite veins which cut through altered rhyolite of the Rooiberg Group, which is surrounded by the Bushveld Complex granite.

Buffalo fluorite mine was mothballed in October 2008 due to market circumstances. Ongoing empirical test work to reduce the phosphorous content of its product was in progress.

In addition, test work on the fines from the substantial aggregate dumps on the neighbouring property continued. If either of these projects are revived and proves successful, Buffalo could be re-opened.

One of the opportunities at Buffalo that Sallies Ltd, the previous owner, planned to investigate further was the rare earth minerals contained within tailings.
During 2009 Firebird Global Master Fund, Ltd (Incorporated in the Cayman Islands) made a successful offer for the shares that they did not already owned.

The Zandkops Drift Complex

The pipe-like vermiculite-calcite-limonite body, similar in character to deeply weathered complexes like Mount Weld in Australia, is located approximately 26 km southwest of Garies, in the Northern Cape.

Pyrochlore and secondary REE mineralization is associated with manganoan calcite, goyazite, gorceixite, carbonate-apatite, betafite, uraninite, and niobium rutile.

A bulk sample assayed 2.6% P2O5, 900 ppm Nb, 0.069 kg/t U3O8, 0.197 kg/t ThO2, 1.2 %REO+ThO2 and 320 ppm Mo, but beneficiation tests yielded disappointing results.


Zambia

  •  Aim-listed African Consolidated Resources (ACR) has signed a joint-venture (JV) agreement with an Australian-based exploration company Rare Earth International (REI) to explore ACR’s Nkombwa Hill rare-earths and phosphate project, in Zambia.

    The 720-km2 exploration project was expected to contain a large potential phosphate resource, as well as light rare-earth elements (REEs).

    REI would, in terms of the agreement, spend at least $750 000 over the next two years to define an inferred resource to a Joint Ore Reserve Committee- (Jorc-) compliant standard for the project, in order to earn a 30% stake.

    It would then spend a further $600 000 over an 18-month period to define an indicated resource to Jorc-compliant standard, the completion of which would lead to an increase in its stake to 50%.

    ACR would then have the option to cofund the completion of a prefeasibility study and a bankable feasibility study, with each party maintaining a 50% interest in the project.

    However, if it decided not to provide cofunding for the feasibility studies, REI would eventually boost its stake in the project to 75% by providing all the funding.

    Corporate finance services provider Ambrian Capital said in a research note that the signing of the JV partnership was a “savvy” move, as it would allow the company to diversify out of its primary country of operation, Zimbabwe.

    Further, Ambrian pointed out that while the project’s focus would be phosphate, for which there was plenty of demand in Africa, it would also bring in more experienced partners to focus on the development of the more lucrative REEs.

    “There is currently a significant focus on REEs following recent moves by China, the world’s largest supplier or REEs, to restrict exports,” it added.

    China plans to allow only a few State-owned enterprises to mine rare-earth metals, as part of a campaign to combat illegal mining and to consolidate its reserves.

    Worldwide demand for REEs, which are used in the manufacturing of hybrid cars, superalloys used in the defence industry, cellphones, large wind turbines, missiles and computer monitors, is on the increase, but the majority of the world’s supply, 95%, was still produced by China.

    Global demand for REEs was expected to exceed 200 000 t/y by 2014, while a global shortfall of 40 000 t/y was expected by 2015, the US-based Institute for the Analysis of Global Security pointed out in a March report.

    This has led to companies relooking at old dormant REEs projects.

    Australia’s Lynas Corporation was developing one of the largest REE projects outside China, namely the Mount Weld carbonatite in Western Australia, while US-based Molycorp Minerals had an interest in another large REE resource.

    TSX Venture Exchange-listed Great Western Minerals Group also announced earlier this month that it had been granted new-order mining rights for the Steemkampskraal monazite project, in South Africa’s Western Cape province. (Source: 
    miningweekly.com)