Wigu Hill

Wigu Hill, Tanzania

The Wigu Hill Rare Earth Element (“REE”) Project is a light rare earth element deposit and a large carbonite complex with bastnaesite mineralization. The licence area covers 142km2. Initial grab samples yeilded results as high as 27.25% TREO. Montero released an initial NI 43-101 Inferred resource estimate of 3.3Mt at 2.6% LREO5 including 510K @ 4.4% LREO5 on 2 of 10 possible drill targets. Further exploration drilling to add to the current resource is underway. Click the title to download and view the NI-43-101 Report

Montero revised a portion of its initial NI 43-101 compliant Inferred Mineral Resource estimate of 3.3M tonnes at 2.6% LREO5 (Light Rare Earth Oxides) for the Tembo and Twiga Zones. The updated resource estimate is only for the Twiga Zone and is based on data from the initial 15 core boreholes (1,560m) used in the initial resource estimate and data from infill drilling of 17 boreholes at 25m intervals (986m) completed in 2012. The data used in the revised Twiga Zone overall resource has outlined a higher grade REE deposit for this zone on the south-eastern ridge of the Wigu Hill carbonatite complex. A total Inferred Mineral Resource of 1.9 M tonnes at a grade of 2.7% LREO5 has been estimated from the preliminary and infill drilling of 32 boreholes (2,546m) for the Twiga Zone to a depth of 50m. A sensitivity analysis at a cut-off grade of 3% LREO5 has shown that the Inferred Mineral Resource contains a higher-grade portion consisting of 0.47 M tonnes averaging 5.2% LREO5. The independent estimate was prepared by AMEC Earth & Environmental Services (UK) Limited (AMEC). See full news release.


The carbonatite complex has been know since the 1950s and sampled many times by various mining and scientific organisations. A summary is listed below:

Early 1950 – discovery of the deposit by the geological survey

1957 – New Consolidated Goldfields examined the hill for rare earth

1973 – The area was explored by Molycorp Minerals

1987 – Tanzanian-Canadian Agrogeology project examined the area for phosphate potential

2000 – The area was examined by P.R. Siegfriend

2007 – BGR assessed the project on behalf of the Tanzanian government

2008 – Montero entered into an agreement with RSR in 2007

2009 – Reconnaisance sampling and mapping of the Wigu Hill complex commenced

2011 – Montero listed on the TSX.V in February and exploration commenced 

2011 –NI43-101 Resource reported and metallurgical test work underway

2015 – Montero awarded a Retention License over the Wigu Hill Deposit and project put on care-and-maintenance

2017 – Government of Tanzania review all current licenses in Tanzania

2018 – All Retention Licenses revoked by Government decree and currently under review by Montero


The Wigu Hill Property is a large, REE enriched carbonatite with dolomitic vein system which cut into Precambrian gneisses. The deposit type would be best described as a high level, carbonatite hosted REE dike deposit. The principally coarse-grained carbonatite dikes largely contain dolomite, bastnaesite and quartz.

Mineralization is mainly concentrated in the carbonatite dykes although the surrounding country rocks appear to have low grade REE mineralization of unknown extent and grade. The REEs occur predominantly in the minerals bastnaesite, monazite and synchysite, although others such as parasite and goyazite have also been encountered. The carbonatite dykes that host the REE are typically 0.6-8.0m wide and can be traced intermittently over distances of over 700m. The deposit is a LREE dominated which is characteristic of most carbonatites. Sampling to date has revealed grades averaging over 7% total rare earth oxide (TREO), with individual samples up to 26.2% TREO.


Exploration to date has revealed the delineation of 2 defined shallow resource areas and at least 3 additional potential resource target areas that have seen geological mapping, trenching and drilling, namely: Twiga, Tembo, and Tumbili, Lower Nyati and Upper Nyati, respectively;


Inferred Resource of 3.3 M tonnes at 2.6% TREO at the Twiga and Tembo targets (by AMEC, refer news releases September 12, 2011, October 24, 2011);

Inferred Resource at the Twiga Target of 1.9 M tonnes at a grade of 2.7% LREO5 (Light Rare Earth Oxide) from the preliminary and infill drilling of 32 boreholes (2,546m). See news release.

Inferred Mineral resource at the Twiga Target contains a higher-grade portion consisting of 0.47 M tonnes averaging 5.2% LREO5 to a depth of 50m and cut-off grade of 3% LREO5 (refer news release August 6, 2013). This was based on 32 core boreholes (2,546m) at 25m intervals. This outlined the potential for a small high-grade open pit mining operation within the larger resource (detailed in an independent technical review by Turgis Consulting).


Lower Nyati target – mapping, grab sampling (refer news release April 2, 2012, April 12, 2012), trenching and initial core drilling of 1030m at 100m intervals (refer news release April 10, 2012) at the Lower Nyati Target have identified a potential REE resource target of 20 million tonnes. A proposed core-drilling program of 20 infill and exploration drill holes (5,200m) was designed and access roads and drill pads constructed.

Upper Nyati target – geological mapping and grab sampling have shown that the REE mineralisation on the Lower Nyati Target extends to the Upper Nyati target to the top of Wigu Hill.

Tumbili target – mapping, trenching (1,190m) and drilling (1,525m) have identified a potential high grade REE resource target in the western portion of the Tumbili Target.

The Wigu Hill Rare Earth Project does not contain a mineral reserve and is not currently in production. Any decision to place the Wigu Hill Rare Earth Project into production requires the support of a feasibility study prepared in accordance with National Instrument 43-101. At this time the Company has completed a series of laboratory and pilot scale testwork, but this does not satisfy the requirements of a feasibility study. Accordingly, any decision to commence production on the Wigu Hill Rare Earth Project is neither imminent nor assured, and investors cannot assume that the Wigu Hill Rare Earth Project hosts an economic mine at this time.

In early 2011, Mintek initiated a Hydrometallurgical Refinery testwork program to develop a leaching and extraction process for the production of high purity rare earth saleable chemical products. Details are outlined below.

Metallurgy, on Wigu Hill material

An update on the mineral processing and metallurgical testwork performed to date on the bastnaesite-rich carbonatite material from the Wigu Hill Rare Earth Project in Tanzania. In early 2010, Montero approached Mintek, an internationally recognized metallurgical research and testwork facility in Johannesburg, South Africa, to test the Wigu Hill carbonatite for recovery of Rare Earths. Mintek has over 25 years of experience working performing research and testwork developing economic process routes for various Rare Earth mineralizations.

Montero’s strategy is to become the first Rare Earth (“REE”) materials producer in Africa which required embarking on a series of early-stage metallurgical testwork on the mineralised carbonatite material from Wigu Hill. Early in 2010, the initial mapping of Wigu Hill demonstrated a potential for a significant REE mineralized system. The major challenge would be the mineral beneficiation, hydrometallurgy, and production of saleable rare earths. A research program to identify, test and determine the critical path to rare earth production was the justification for starting the testwork in parallel with such an early stage in the exploration program. In 2010, Montero established a team led by Mike Evans that worked with Mintek on an extensive literature research program to identify:

  1. a minerals processing route to produce a bastnaesite mineral concentrate and 2) a hydrometallurgical process route for the production of saleable rare earth products. Montero delivered the first representative bulk sample to the Mintek facility in Johannesburg on June 2010 followed by a second sample in July 2011. These unweathered, course grained bastnsite-rich samples were taken from trenches and pits in the Twiga and Tembo Zones where Montero has subsequently completed a NI 43-101 Inferred Resource Estimate (see news release dated 12/09/2011).
    1. Preliminary Minerals Processing Testwork to produce a bastnaesite mineral concentrate
      The basnasite-rich samples from Wigu Hill were initially sent for mineralogical analysis, crushed, assayed by element and chemical analysis, and then subjected to a mineral processing testwork program which included tests such as; screening, gravity separation, magnetic susceptibility, X-ray sorting, and flotation. The objective was to upgrade the run of mine (ROM) mineralized carbonatite material to a bastnäsite-rich mineral concentrate. This mineral concentrate potentially could be sold “as is” to downstream REE processors, or alternatively, become a feed stock to a hydrometallurgical refinery designed to process this bastnäsite concentrate into a variety of saleable rare earth chemical products. At present, this testwork program on mineral processing remains in progress.
  2. Preliminary Hydrometallurgical Refinery Testwork to produce saleable Rare Earth chemicals
    The detailed literature work enabled the team to develop a hydrometallurgical flowsheet with a two-stage Rare Earth Refinery recovery process;Stage 1 Refining – The leaching of the bastnäsite mineral concentrate from the mining and mineral processing plant followed by a precipitation stage to produce a Mixed Rare Earth Oxide (“MREO”) or chloride saleable product, and;Stage 2 Refining –The continued processing of the MREO concentrate solution and the extraction via Solvent Extraction (SX) and/or Ion Exchange (“IE”) technology to separate the individual REE’s.To view a conceptual illustration of the flowsheet currently being evaluated click here

Stage 1 Refinery Testwork

Leaching tests were performed using a variety of leaching lixiviants. From this testwork program, it was determined that a leach process using hydrochloric acid (“HCl”) was the most efficient for the Wigu Hill bastnäsite-rich material. Acid consuming gangue material is dissolved using hydrochloric acid in order to expose the bastnäsite-rich material. The residue is then leached with caustic soda to remove the silica and expose the rare earths minerals for subsequent dissolution in a further hydrochloric acid leach. Following the success of this initial test work program, a second stage program was completed, and more recently, a third stage of leaching tests is currently being performed to provide further optimization information for the leaching process. The third stage optimization tests will provide a definitive process route for the leaching of the Wigu Hill mineralized carbonatite.

The results to date are encouraging. In addition to optimizing the main leaching processes, the testwork program included detailed mineralogy of the residues from the various process stages. Testwork also evaluated the potential for recycling the spent hydrochloric acid and caustic soda reagent streams, modelling the process with SysCAD mass balance software. SysCAD was used to model the bulk leaches and the phases to produce a MREO saleable product. The final product of this process will also provide a feed solution for the Stage 2 Refining testwork.

Stage 2 Refinery Testwork

Montero and Mintek will embark on a testwork program that will commence in early 2013 to define the process route to take the MREO feedstock and produce individual, pure rare earth chemicals. On completion of this testwork program, the target is to complete a feasibility study for the Stage 2 Refinery and the upgrade of the Stage 1 Refinery to a larger production of REE chemicals.

The Stage 1 hydrometallurgical Refinery optimization testwork is targetted for completion by year end and presented by Mintek for evaluation by Montero. This will generate sufficient data to form the Design Basis for a Feasibility Study. The deliverables of this feasibility study will be a “Demonstration Plant” for a Leaching and Mixed Rare Earth Oxide (“MREO”) refinery facility targeting the production of 3,000-5,000 tpa of MREO chemical products for sale. The facility will also provide pregnant solution for solvent extraction testwork leading to the Feasibility Study of the Stage 2 Refinery that will target production of the individual rare earth chemicals for sale.

Montero has an expert metallurgical and hydrometallurgical team to undertake this work.


Phosco, South Africa


The Phosco project covers two phosphate exploration projects in South Africa, namely Duyker Eiland and Phillips Kraal in the Western Cape (see maps on left sidebar). Exploration drilling has been completed on Duyker Eiland and Phillips Kraal. Resource definition on Duyker Eiland has been completed and an NI43-101 compliant resource report has been compiled by an independent consultant, AMEC.

The most advanced project, Duyker Eiland, is located 30 kilometers north of the Port of Saldanha, in the Western Cape Province of South Africa.


The phosphate deposits are located around Saldanha Bay in the Western Cape, and more detailed studies were conducted in the early 1900’s. A phosphate deposit was mined until recent years by Samancor at Langebaanweg, about 25 km southeast of the Duyker Eiland property, 12 km east of Phillips Kraal. This phosphate was sold for direct use as fertiliser, with some upgrading done by mixing with other components, such as ammonium sulphate.

The Duyker Eiland project area has historical prospecting results of approximately 30Mt of phosphatic sands. In the 1940’s and 1950’s, AMCOR conducted mineral exploration on the property, however these records have been lost. During the 1960’s, African Explosives and Chemical Industries Limited (AECI) conducted drilling and pitting on a 3.0 km by 0.5 km area extending over the property. AECI conducted flotation tests and obtained a concentrate with 33.0 % P2O5 (87 % collophane). These estimation and flotation results are historical in nature, and do not comply with NI 43-101 definitions. Historical prospecting results are also published for the area of the Phillips Kraal project though the records have also been lost.


The regional geology is marked by the presence of Tertiary/Quaternary sediments consisting of calcareous and aeolian sands, calcretes and phoscretes.

At Duyker Eiland, a portion of the Vredenburg granitic pluton is overlain by sediments of the Varswater formation, which is part of the Miocene-Pliocene Sandveld group, and limestones and calcarenites of the Pleistocene Langebaan formation.

Sands, clayey sands and gravels of the phosphate-bearing Varswater formation sediments are partially overlain by limestones of the Langebaan Formation, which is exposed on top and along the shoulders of the small hill that dominates the topography of the area. The phosphate mineralization occurs as rounded and sub-rounded,polished collophane grains. A similar geologic setting is observed at the Phillips Kraal project. Desktop studies indicate that historic targets at Lamberts Bay also occur in the Varswater Formation. The Bierkraal project area is located in an apatite rich layer of the Bushveld Igneous Complex.

Exploration Programs

The initial exploration program included, the compilation of the historic data, desktop studies, field visits and mapping and was followed by RC/Aircore drilling at Duyker Eiland and at Phillips Kraal during the 2011 exploration campaign.

In late 2011, the Initial Inferred Mineral Resource of 32.8 M tonnes grading 7.15% P2O5, at the Duyker Eiland property was announced.  This resource is capable of producing an acid-grade phosphate concentrate of 33% to 35% P2O5 (see news release 16/11/2011) Click the title to download and view the N1 43-101 Resource Estimate.

Preliminary Economic Assessment

An independent NI43-101 compliant PEA has been completed by Turgis Consulting on the Duyker Eiland Phosphate Project in South Africa. Positive results and highlights are as follows:

  • A NPV of CAD$ 126.1 million (at a discount rate of 10%) and an IRR of 38.14%
  • Average 4.5 million tonnes per annum rock mined at low stripping ratios of 0.57:1
  • Average production of 490,000 tonnes per annum of 33% P2O5 concentrate
  • 11 year Life of Mine (based on initial resource estimate)
  • Operating cash costs CAD$ 109 per tonne concentrate Free alongside Ship (“FAS”) at the port of Saldanha, South Africa
  • Capital costs of CAD$ 132 million

Click the title to download and view the N1 43-101 Compliant PEA.