Greenhills Resources represents Bushveld Minerals’ tin platform containing a pan-African portfolio of low-cost open-cast deposits in historically tin-producing regions, with a near-term production profile. The three assets in the portfolio are the Uis Tin Project in Namibia and the Mokopane and Marble Hall Tin Projects, both located in South Africa.
Greenhills Resources is an attractive stand-alone platform with quality strategic partners and a strong dedicated management team to deliver long-term shareholder value. Greenhills Resources aims to capitalise on the solid supply/demand fundamentals of tin by developing a critical mass of tin resource inventory and achieving production in the near term and further scaling up production by consolidating tin assets in Africa.
THE TIN PROJECTS
The Mokopane Tin Project
The Mokopane Tin Project comprises prospecting rights over five farms on the northern limb of the Bushveld Complex, where four tin mineralisation targets have been identified. A fifth target is on an additional licence, which is the subject of the Company’s prospecting right application. The five targets are all in close proximity to each other and comprise open-cast tin deposits hosted in granites. The mineralisation is disseminated cassiterite hosted in granite rocks of the Bushveld Complex, and is easily beneficiated using gravity-based methods such as spirals and shaking tables. Metallurgical test-work has demonstrated good recoveries in excess of 70% for a concentrate grade of 74.59% SnO2.
The two deposits combine for a total resouce of 18,447 tons of contained tin, made up as follows:
- Groenfontein deposit (at a 0.1% Sn cut-off) with 5,995 tons of contained tin comprising mineral resources of 3,095,000 tons at 0.15% Sn (4,792 tons contained tin, Measured and Indicated) and 898,000 tons at 0.13% Sn (1,203 tons contained tin, Inferred)
- Zaaiplaats Deposit (at a 0.07% Sn cut-off) with 12,452 tons contained tin comprising mineral resources of 1,231,000 tons at 0.09% (1,110 tons contained tin, Indicated) and 10,503,000 tons at 0.108 % Sn (11,342 tons contained tin, Inferred)
A scoping study was completed in August 2014 confirming a base case production scenario of 691,000 tons run-of-mine processed into 1,380 tons per annum of 51.4% Sn concentrate, which would be smelted to produce approximately 700tpa of 99.5% Sn metal. The base case produced a pre-tax NPV of US$18 million and a pre-tax IRR of 49.8% with a payback period of two years from commissioning at a capital spend of US$16.7 million. Unit cash operating costs were estimated at US$14,276/mt against a forecast tin price of US$22,928/mt Sn. Should the project only produce a concentrate product, the operating costs would be US$6,902 per ton of Sn concentrate (equivalent to US$13,482 per ton Sn metal contained) and the capex would be reduced to US$16.6 million.
Marble Hall Tin Project
The Marble Hall Tin Project comprises a prospecting right over four farms surrounding the Vlakfontein tin mine in Limpopo province, South Africa. An application to extend the prospecting area to include the additional portions of the identified mineralisation is yet to be finalised. The project hosts mineralisation in a 1m–8m-thick gently dipping breccia. Historical drilling work sourced from Gold Fields Ltd includes 60 boreholes, which intersected significant mineralisation at relatively shallow depths of over 200m and recorded grades of 1.27% SnO2 over 5m, 0.47% SnO2 over 2m and 0.53% SnO2 over 3m. A potential (non-JORC) resource of 3.75Mt at 0.32% SnO2, representing 12,000 tons of contained tin, was calculated historically but the project was not pursued by Gold Fields.
The Uis Tin Project
The Uis Tin Project is one of the largest undeveloped open-cast hard rock tin deposits in the world and has a history of significant tin production. The project is located in the Erongo Region of Namibia and comprises three mining licences: ML 134, ML 129 and ML 133. Historic work suggests potentially significant tin resources on these licences, the largest of which is a historical estimate (non-JORC) of 70.3Mt at 0.14% Sn for a total potential resource of over 90,000 of contained tin within ML 134. In addition to this, ML 134 also contains the old Three Aloes Mine which is known to have produced tantalum concentrate in the past. ML 133 contains the old Nainais Tin-Tan Mine and ML 129 hosts the C1 and B1 pegmatites, which have small surface workings created by artisanal miners.
Due diligence confirmed large mineralised pegmatite ore bodies with localised samples of over 0.3% Sn commonly found in greisenised zones. Greenhills Resources intends to confirm a JORC-compliant resource and advance feasibility studies, while simultaneously refurbishing the old existing plant for a 10 tons per hour pilot scale production of tin concentrate. During this time Greenhills Resources resources intend to evaluate the potential to increase plant feed grade through various ore sorting methods and targeting potential higher-grade zones.
The following work has been completed to date:
- Detailed geological mapping of eight previously mined pits at the Uis Tin Project within ML134 (containing over 12 pegmatite bodies) to characterise and delineate the higher-grade greisenised portions of the ore-body. An exploration target of more than 20,000 tons of contained tin will be the focus of further work (including drilling).
- Grab sampling of pegmatites in the various licences (ML129, ML133 and ML134), with tin grades of over 0.6% Sn reported and numerous samples with over 0.3% Sn.
- Size grading analysis of pegmatite from the V1/V2 pit within licence ML134 (containing the largest pegmatite body identified thus far), which shows that much of the cassiterite (SnO2) is coarse and may be liberated as relatively large particle sizes (over 250 µm), and that classification of the ore into various size fractions could improve recovery efficiency in the plant.
- Dense media separation (DMS) tests which showed that clean, saleable concentrate grades are achievable via a single stage of DMS, and that excellent separation occurs at a density of 2.90 and at coarse size fractions of -6 mm, with recoveries of over 70% achievable.
The results of this work will inform the exploration programme at the Uis Project, with the aim to drill and define a JORC-compliant resource. An existing pilot plant at the Uis Mine is currently being used to test gravity separation using jigs, spirals and shaking tables, with over 2 tons of cassiterite concentrate produced thus far. The size grading analysis results will help to improve the flowsheet at the plant and to further optimise recoveries at a pilot-scale. Additionally, the DMS results have indicated the suitability of DMS as a recovery method for the Uis cassiterite, and the intent is to incorporate a DMS plant into the pilot plant and to run this plant on a continuous basis, aimed at demonstrating the techno-economic parameters for a larger plant.
Bushveld has an interest in the Uis Project through its 49.5% shareholding in Dawnmin Africa Investments Ltd (“Dawnmin”), which has a 85% shareholding in Guinea Fowl Investments 27 (Pty) Ltd (“Guinea Fowl”), while the remaining 15% shareholding is held by the Small Miners of Uis, a Namibian Government entity.