This report presents an updated Mineral Resource estimate and preliminary metallurgical testwork results for the K-Hill manganese project, supported by drilling data collected from April 2018 to July 2021.
Report context
SRK Consulting completed an update of the Mineral Resource Estimate for the Kgwakgwe Hill Manganese Project, based on drilling data collected by Giyani from 16th April 2018 to 19th July 2021 inclusive. The Mineral Resource is classified according to the CIM Best Practice Guidelines and reported in accordance with the 2014 CIM Definition Standards. The estimate incorporates an updated block model constrained by an updated optimised pit shell, with domain modelling undertaken in Leapfrog Geo and estimation in Leapfrog Edge. The Qualified Person responsible for the Mineral Resource Statement is Dr Lucy Roberts, MAusIMM(CP), a Principal Consultant (Resource Geology) with SRK.
Processing route
Proposed flowsheet and product
The metallurgical studies, based on testwork completed by Lab 4 Inc. and Dalhousie University, indicate that the mineralised material is amenable to reductive acid leaching and can be processed using a flowsheet that consists of an acid leach followed by solution purification, solvent extraction and vacuum crystallisation for the production of a high purity manganese sulphate monohydrate product (HPMSM) suitable for sale into the battery market. The ongoing metallurgical testwork and updated plant design will focus on a slight modification to the planned flowsheet in order to produce HPMSM, building on earlier work that targeted High Purity Electrolytic Manganese Metal (HPEMM).
Mineralogical testwork
Dalhousie University undertook mineralogical analysis on a selection of manganese oxide bearing rocks taken as grab samples from K-Hill mineralisation. Four samples were tested to determine the mineralogical composition. Identified mineral species included cryptomelane, hausmannite, hollandite, psilomelane, pyrolusite, jacobsite, and coronadite. The manganese minerals occurred in three forms: as staining on silicates, iron oxides and as themselves; as small veins where manganese oxides have been deposited on each other particularly within well fissured zones; and as nodules where the Mn has built up into botryoidal masses that may contain other minerals within them.
Head assays reported for the mineralogical samples showed MnO grades ranging from 4.3% to 60.8%. Samples tested included dump material (48.7% MnO), altered shale (48.8% MnO), silicified shale (4.3% MnO), and shale with kaolin (60.8% MnO).
Leach testwork
Dalhousie University conducted run of mine acid leach tests with sucrose added as a reductant on three samples from a single drill hole, plus baseline leach tests without reductant addition. Test conditions included a grind size P80 of 200 µm, sample mass of 25 g, acid concentration of 260 g/l H2SO4, temperature of 90°C, and retention time of 3 hours.
Results showed that the reductant significantly improved Mn extraction and leach kinetics. For sample MT10, Mn extraction with reductant ranged from 87.7% to 91.7% compared to 2.9% to 3.2% without. For sample MT11, extraction with reductant ranged from 83.1% to 93.9% versus 0.4% to 2.3% without. For sample MT12, extraction with reductant ranged from 94.6% to 100.5% versus 1.8% to 2.3% without. The testwork programme did not evaluate other possible reductants such as SO2, which is used in acidic sulphite reduction processes at several operating plants.
Solution assays from the leach tests indicated co-extraction of metals including Fe (6,589 mg/l), Al (938 mg/l), Cu, Zn, Ni and Co as sulphates. The report notes that the solution can be purified by removing Fe and Al sulphates as hydroxides via precipitation with lime, with further purification by removal of base metals as sulphides via precipitation with sodium hydrosulphide.
Solvent extraction testwork
Solvent extraction tests were conducted by Dalhousie University on pregnant leach solution using the organic extractant D2EPHA. Results indicated that approximately 96% of Mn could be extracted by D2EPHA into the organic phase. The report notes that these tests were not optimised but conducted as a standard scoping test, and that 98.5% Mn extraction is assumed for this study, to be verified during future test work. The loaded organic solvent can be stripped with concentrated H2SO4 to produce a concentrated manganese sulphate solution, with the sulphate recovered by vacuum crystallisation to produce HPMSM product.
Comminution testwork
The report states that comminution test work was not completed. This means important design parameters such as Bond Ball Mill work index must be assumed for process development and estimation work.
Key reported parameters
| Parameter | Value | Units | Basis |
|---|---|---|---|
| Overall Mn metallurgical recovery | 90.7 | % | Calculation from testwork and assumptions |
| Leach extraction (with sucrose reductant) | 93.3 | % | Testwork |
| Mn recovery – Fe & Al precipitation | 99.9 | % | Assumption |
| Mn recovery – base metal precipitation | 99.8 | % | Assumption |
| Mn recovery – solvent extraction | 98.5 | % | Assumption |
| Crystallisation efficiency | 99.0 | % | Assumption |
| Leach test – grind size P80 | 200 | µm | Testwork condition |
| Leach test – acid concentration | 260 | g/l H2SO4 | Testwork condition |
| Leach test – temperature | 90 | °C | Testwork condition |
| Leach test – retention time | 3 | hr | Testwork condition |
| Indicated Mineral Resource | 1.6 | million tonnes | Within optimised pit shell, >7.3% MnO |
| Indicated MnO grade | 22.0 | % | Block model estimate |
| Inferred Mineral Resource | 1.4 | million tonnes | Within optimised pit shell, >7.3% MnO |
| Inferred MnO grade | 13.9 | % | Block model estimate |
| Pit optimisation – HPMSM price | 1,588 | USD/t CFR Japan/Korea | 2020 market data |
| Pit optimisation – marginal cut-off | 7.3 | % MnO | Calculated from parameters |
| Pit optimisation – total process recovery | 90.7 | % MnO | Applied for pit optimisation |
| Pit optimisation – mining recovery | 98 | % | Applied for pit optimisation |
| Pit optimisation – dilution | 3 | % | Applied for pit optimisation |
| Pit optimisation – overall slope angle | 41 | degrees | Applied for pit optimisation |
| Pit optimisation – mining cost | 3.46 | USD/t rock | Applied for pit optimisation |
| Pit optimisation – processing cost | 213.0 | USD/t RoM | Applied for pit optimisation |
| Pit optimisation – G&A | 20.0 | USD/t RoM | Applied for pit optimisation |
| Core recovery – Upper Mn Shale (DD program) | 41 | % | Measured average |
| Density – A2 domain (SET 2, wax coated) | 2.14 | g/cm³ | Average of 14 samples |
| Density – B domain (SET 2, wax coated) | 2.32 | g/cm³ | Average of 4 samples |
| Block model cell dimensions | 25 x 25 x 1 | m | Parent cells |
| Minimum composites per block estimate | 4 | , | Estimation parameter |
| Maximum composites per block estimate | 12 | , | Estimation parameter |
Project website: https://ca.finance.yahoo.com/news/giyani-metals-advances-k-hill-123900034.html
Technical qualifications
The report identifies several specific limitations and data quality considerations:
- Core recovery from the diamond drilling program within the Upper Mn Shale unit averages 41%, and confidence in the accuracy of individual assay grades is reduced as a result. No clear relationship has been identified between core recovery and grade.
- Density data is limited. The most reliable dataset (SET 2, wax coated dry samples) contains only 49 samples, and no corresponding MnO assays exist to establish a correlation between MnO grade and density. SRK considers the limited quantity of appropriate dry density data a potential risk to the reported Mineral Resource.
- Comminution test work was not completed, meaning important design parameters such as Bond Ball Mill work index must be assumed for process development.
- The metallurgical testwork programme did not evaluate other possible reductants such as SO2.
- Direct metallurgical testwork has not been undertaken on material from the B and C horizons. Initial geological observations suggest the material is lithologically similar to the A horizons, but processing characteristics remain unknown until detailed testwork is completed.
- The solvent extraction tests were not optimised but conducted as a standard scoping test.
- A portion of the mineralised domains at the margins have not been classified where poor geological and drilling support exists.
- Artisanal mining depletion has been applied based on GPR and laser rangefinder surveys, but it is possible that unidentified workings with obscured accesses exist and have not yet been captured.
*Source: SRK Consulting K-Hill MRE Update – Main Report, October 2021, Sections 13 and 14.*
