Preliminary Economic Assessment effective 15 December 2012, describing a two-site processing route: a mine-site RECl plant producing mixed rare-earth chloride solution, and a separate RE Separation Plant producing individual rare-earth oxides.
Report context
This profile is based on the Preliminary Economic Assessment (PEA) for the Steenkampskraal Project, prepared by Snowden Group for Great Western Minerals Group Ltd. (GWMG) and Rare Earth Extraction Co. Limited, with an effective date of 15 December 2012. The technical report covers two processing facilities: the RECl Plant at the Steenkampskraal mine site, and a downstream RE Separation Plant. The former produces a mixed rare-earth chloride solution; the latter separates and purifies individual rare-earth oxides. The study is conceptual, with one section (hydrometallurgical processing) qualitatively tested, and the tailings retreatment process based on external research without site-specific verification.
Processing route
Mine-site RECl plant
The RECl Plant at Steenkampskraal extracts rare earths from run-of-mine (RoM) material using comminution, concentration, and hydrometallurgical leaching. The plant is nominally designed to treat 70,000 tonnes per annum of RoM feed, with a nominal operating range of 30,000 to 44,000 tonnes per annum depending on dilution and mined grade, producing 5,000 tonnes per annum of total rare earth oxide (TREO) as a mixed chloride solution.
RoM material, delivered at a nominal top size of 300 mm, is crushed and screened, with an option for sorting to reject waste rock. The 'accepts' stream undergoes secondary crushing in closed circuit, with final product reporting to a ball mill feed hopper. Ball mill product is classified via cyclones, with overflow to the concentrator and underflow recycled.
Concentration uses three-stage wet low-intensity magnetic separation, removing magnetite and ilmenite from the non-magnetic REE-bearing stream. The REE-rich fraction then undergoes sulphide flotation to remove sulphide minerals (typically chalcopyrite, pyrite, galena); the sulphide concentrate may contain economic copper, gold, and silver, with recovery to be investigated in future studies. Sulphide flotation tails proceed to monazite flotation, designed with multiple stages of cleaning, recleaning, and scavenging due to expected high mass pull. The monazite concentrate undergoes acid digestion to selectively leach apatite and other impurities, followed by liquid-solid separation and solids washing.
Washed solids are reground and dewatered prior to hydrometallurgical processing. The classified regrind product is pumped to caustic cracking tanks, converting rare-earth phosphates to hydroxides, followed by water leach/wash and liquid-solid separation to form a tri-sodium phosphate (TSP) solution and solid RE hydroxide. TSP may be recovered as a by-product via crystallisation, allowing caustic and water recycle. The RE hydroxide is leached with hydrochloric acid at controlled pH to prevent thorium dissolution, filtered, and washed. Residual solids are stored pending disposal or recycle; the solution undergoes radium removal by precipitation. The clarified mixed RECl liquor, approximately 230 g/ℓ TREO, is stored for road transport by dedicated tankers to the RE Separation Plant.
Tailings retreatment
After RoM resource depletion, the plant will be modified to reclaim and process surface tailings dams. The existing ball mill will be used with modified operational parameters. Milled slurry is concentrated using a combination of wet high- and low-intensity magnetic separation to remove residual magnetite, ilmenite, apatite, and gangue. The tailings process replaces acid roasting with an elevated temperature sulphuric acid leach, converting phosphates to water-soluble sulphates, followed by ambient water agitation, filtration, and washing. RE sulphates are precipitated as double salts and separated from sodium sulphate solution, which may be recovered for sale or reuse. Precipitates are converted to RE hydroxides by caustic addition before reporting to the main RoM circuit.
This tailings process is based on research on monazite concentrate from the Hoidas Lake deposit in Canada, reported by the Guangzhou Research Institute of Non-Ferrous Metals in June 2012. No testwork has been performed to verify metallurgical performance for Steenkampskraal tailings specifically. Most main plant equipment is intended for reuse, with wet high-intensity magnetic separation equipment requiring installation.
RE Separation Plant
The RE Separation Plant, located approximately 1 km west of the Vredendal North residential area, within the Matzikama Local Municipality, will separate and purify the mixed RECl solution. Nominal capacity is 5,000 tpa TREO as mixed chloride solution at 230 g/ℓ. The process uses solvent extraction, with initial stages removing residual iron, followed by selective extraction of medium and heavy rare earths (Sm, Eu, Dy, Gd, Tb, Y), leaving light rare earths (La, Ce, Pr, Nd) in the aqueous solution.
Light rare earths are separated individually via solvent extraction into La, Ce, and mixed Pr/Nd chlorides, precipitated, filtered, washed, and calcined in a tunnel kiln to produce oxides. Heavy rare earths are separated into individual Sm, Gd, Tb, Dy, Y products; an Eu-rich Sm+Eu+Gd stream is treated separately using alkali reduction to produce high-purity Eu oxide. A mixed heavy rare earth concentrate is produced for maximum economic extraction. Final products are screened, blended for consistency, and packaged to customer specification. Final product purities range from 2N5 to 5N, with recoveries of 88–94% per product (Table 15.10). The process is designed as a zero water emission site.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| RECl Plant feed rate | 70,000 | tpa RoM | Design |
| RECl Plant operating range | 30,000–44,000 | tpa RoM | Design |
| RECl solution TREO concentration | 230 | g/ℓ | Target specification |
| RECl solution pH | 2–3 | , | Target specification |
| SO₄²⁻ | ≤100 | ppm | Target specification |
| PO₄³⁻ | ≤100 | ppm | Target specification |
| Fe₂O₃ | ≤200 | ppm | Target specification |
| CaO+MgO | ≤3.0 | % | Target specification |
| Al₂O₃ | ≤0.1 | % | Target specification |
| SiO₂ | ≤200 | ppm | Target specification |
| PbO | ≤30 | ppm | Target specification |
| ZnO | ≤50 | ppm | Target specification |
| CuO | ≤50 | ppm | Target specification |
| NiO | ≤50 | ppm | Target specification |
| ThO₂ | ≤10 | ppm | Target specification |
| UO₂ | ≤10 | ppm | Target specification |
| RaO | ≤10 | ppm | Target specification |
| Specific radioactivity α+β | ≤1 | Bq/g | Target specification |
| RE Separation Plant capacity | 5,000 | tpa TREO | Design |
| Mixed RECl feed to separation | 230 | g/ℓ TREO | Design |
| Product purity (individual REOs) | 2N5–5N | % | Design target |
| Product recovery (individual REOs) | 88–94 | % | Design target |
| Total annual operating cost (RECl Plant) | 20.143 | CAD M | Estimate |
| Total capital cost (RECl Plant) | 29.65 | CAD M | Estimate (incl. 20% contingency) |
| Additional on-site processing capital | 42.65 | CAD M | Allowances |
| Total RECl Plant capital | 72.30 | CAD M | Sum of above |
| RE Separation Plant capital (process) | 45.85 | CAD M | Conceptual estimate |
| Additional separation plant capital | 16.21 | CAD M | Allowances |
| Total RE Separation Plant capital | 62.06 | CAD M | Sum of above |
| Tailings retreatment operating cost | 31.22 | CAD M/yr | Estimate |
| Capital estimate accuracy | 35% | ±% | Including 20% contingency |
| Tailings retreatment additional capital | 1.39 | CAD M | Including 20% contingency |
Technical qualifications
This PEA is a conceptual-level study with a capital estimate accuracy of ±35% including a 20% contingency. The hydrometallurgical process route has been qualitatively tested and reported, but is not verified to pilot or demonstration scale.
The tailings retreatment process has not been tested for Steenkampskraal material; it is based on external research for the Hoidas Lake deposit. The process design substitutes elevated temperature acid leaching for conventional acid roasting. No revenue has been assumed for by-products, including TSP, sodium sulphate, or sulphide float concentrate.
The RE Separation Plant design and capital estimate exclude building costs and import duties, with no blanket contingency. The estimate is based on equipment factorisation and primary estimation. The operating cost estimate for the RE Separation Plant is a summary of an annual cost of CAD30.29 M (labour, power, water, reagents, maintenance, miscellaneous). Reagent supply from local sources has been indicated as feasible.
All radioactive by-products are to be managed under the NNR Act (1999), with a GWMG-appointed Radiation Protection Supervisor. The RECl Plant is designed to produce solution with radioactivity within legal requirements. Waste streams from the RE Separation Plant, including SX barren liquors, crud, and off-gas dust collector solids, are to be returned to the mine site for recycling or disposal in the on-site RCP facility. The RE Separation Plant is designed as a zero water emission site.
Source: *Great Western Minerals Group Ltd. and Rare Earth Extraction Co. Limited, Preliminary Economic Assessment , Steenkampskraal Project*, Project No. J2108, prepared by Snowden Group, effective 15 December 2012, Section 15 Recovery Methods (Sections 15.1–15.4, 15.6, 15.7, 15.8, 15.9, 15.11, 15.12).
