10 Impact Minerals Ltd Annual Report 2023 PRODUCTION OF 4N HPA Playa One’s sulphate metallurgical process has successfully produced >99.99% Al2O3 (nominally 4N HPA) with purities of 99.994% to 99.996% in initial assays. As well as the Al2O3 assay (with all other major elements being below detection), total contaminants are about 41 ppm, representing 99.996% alumina (Al2O3) with the primary contaminants being Fe (2.08ppm), K (7.94ppm), Mg (7.23ppm) and Na (6.61ppm). This compares favourably with the purity of other HPA products published in the public domain (Table 3). Review of Operations continued Note: In table 3 assay methods vary between individual data sources, and direct comparisons should be cautiously viewed. Some elements were omitted for brevity and are reported as “Others_ppm”. Total ppm is the sum of all elements reporting above the detection limit. BDL = below the detection limit. NR = Not Reported. Samples of an example precursor product and final calcined HPA produced using the metallurgical process were analysed using SEM and EDS microscopy by RSC Mineral Consultants, Perth, Western Australia. Precursor salts (before calcination) were imaged as agglomerations of micron-sized particles of alumina. The final calcined HPA product was imaged as corundum crystals and fused aggregates up to 200 microns in size (Figure 8). X-Ray diffraction studies have confirmed that the final product is alpha-HPA, the desired form of alumina. It should be noted that the precipitation of the crystals occurred with little or no control over temperature and pressure. In addition, work has yet to be done on refining the final HPA product, for example, jet milling or developing intermediate saleable products that the end-users require. This critical capability needs to be built out by Impact, and this will be another area of focus in the PFS. Figure 8. Backscattered scanning electron micrographs of final calcined alumina showing corundum crystals and nanoparticles (Sample HY11558). PRELIMINARY ECONOMIC CONSIDERATIONS Playa One has completed a high-level review of the mining and chemical processing costs associated with a preferred development concept of the lake clay-sulphate process. Impact has reviewed this concept in detail and has concluded that it represents a possible compelling path forward to production with the potential to be cost‑competitive with existing and proposed HPA operations within Australia and internationally. Impact is completing the work required to produce a Scoping Study to confirm Playa One’s review. This will include the maiden Mineral Resource Estimate. Playa One KRR FYI Element Sulphuric HPA7 5N As 0.69 NR NR Ag NR NR 0.1 B NR NR NR Ba 0.2 0.516 0.5 Ce BDL NR 0.34 Ca 2.57 <0.06 NR Cr 0.7 2.76 5 Co 0.15 0.046 0.1 Cs 0.02 <0.01 0.03 Fe 2.08 6.2 BDL Gd BDL NR 0.01 Ga 2.01 0.809 NR K 7.94 17.4 NR La BDL NR 0.2 Mg 7.23 0.603 NR Mn 2.74 0.138 1 Mo 0.33 0.052 NR Na 6.61 8.59 0 Nb 0.01 3.01 NR Nd NR NR 0.15 Ni 0.11 0.377 BDL P 3.45 1.74 NR Pb 0.76 <0.01 NR Pr BDL NR 0.04 Rb 0.26 <0.01 0.1 Sc BDL NR 0.1 Si 3.05 15.8 4.67 Sm BDL NR 0.02 Sn BDL NR 0.8 Sr 0.2 0.053 0.2 Ti 0.08 0.695 NR U BDL NR 0.01 V 0.01 <0.02 0.3 W BDL NR 0.1 Zn 0.15 0.488 NR Zr BDL NR NR TOTAL 41.35 59.28 13.67 Table 3. Minor element results for Lake Hope HPA compared with results from King River Resources Ltd (ASX:KRR 25th March 2021, 30th April 2021) and FYI Resources Ltd (ASX:FYI 13th March 2019).
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