Impact Minerals Ltd Annual Report 2023 5 Review of Operations continued GEOLOGY The salt lakes of Western Australia are well known for their unique and complex hydrogeochemistry, which has led to the formation of a wide variety of economic minerals and brines within the playa systems. These include the world-class Yeelirrie uranium deposit (>100 Mlb U3O8), significant resources of potash brines, gypsum and lime-sand. The Lake Hope area was identified by Playa One as having unique climatic and geological characteristics that have resulted in the formation of what is probably a globally unique deposit of aluminium-rich material within the surficial clay layers of two small salt lakes, or “pans”, in the Lake Hope playa system. These pans are called West Lake and East Lake (Figure 3). The lake clays, which are only up to a few metres thick, have unique chemical and physical properties and consist almost entirely of aluminium‑bearing minerals that are plasticine-like in consistency and can be easily sampled with hand-held augers and push tubes (Figure 4). In addition, particle size distribution analysis demonstrates that virtually all the minerals are less than 16 microns in size, and from 60% to 80% of them occur at grain sizes of less than 5 microns (Figure 5). These unique characteristics have produced a near-perfect mineral deposit: a very high-value end‑product whose parent ore is: – very soft and shallow, allowing for extremely cheap free-digging with limited infrastructure requirements, no pre‑stripping, no selective mining, a tiny environmental footprint, and limited rehabilitation requirements. – naturally fine-grained with no need for crushing and grinding, allowing for transport to an off‑site processing facility that can be built on existing industrial sites (Figure 2). In essence, this is Direct Shipping Ore (DSO). – comprised of a few minerals that require only simple washing before acid leaching, thus allowing for low-cost straightforward metallurgical processing. Figure 3. Geology of the Lake Hope Project showing drill hole locations and average aluminium grade on East Lake and West Lake.
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