Core Resources is currently undertaking a comprehensive hydrometallurgical test work program to assist Australian Strategic Materials Ltd (ASM) in the flow sheet development for the Dubbo Project in New South Wales, Australia. This globally significant resource contains high-grades of critical magnetic rare earth elements (MREE), specifically neodymium (Nd), praseodymium (Pr), dysprosium (Dy), and terbium (Tb). Following an evaluation of several processing routes, a hydrochloric acid (HCl) heap leach flow sheet was selected due to its high extraction efficiency and its capability to generate a high-tenor rare earth pregnant leach solution (PLS). This paper discusses and presents the results from the agitated beaker, bottle roll and column leach test work. Initial test work focused on the use of sulfuric acid as a lixiviant, however, due to double salt precipitation causing challenges with variable and low recoveries, hydrochloric acid was selected as the lixiviant for this project. Bottle roll test work primarily investigated the effects of crush size and acid concentration, demonstrating that up to 75.5 per cent of MREE could be extracted from the ore at an acid dosage rate of 48.1 kg/t ore. Column leach test work is briefly discussed in this report with focus placed on a single 8 m column test. Agglomerated ore was used in column leach tests and performance was generally consistent or improved performance when compared to bottle roll tests with high MREE extraction extents and lower acid consumption rates. Work on the development of the final flow sheet continues with a focus on agglomeration optimisation, geotechnical studies and downstream REE processing including impurity removal and rare earth precipitation stages.