Cowalinya Project, Western Australia
The Cowalinya rare earth project is located 70 km SE of Norseman and 110 km NNE of Esperance in Western Australia. It comprises a 253 km2 tenement package (E63/1972, E63/2144, E63/2145) on unallocated crown land hosting dominantly granitic type rocks in the Central Biranup Zone of the Albany Fraser Orogen.
The mineralisation being targeted is shallow, flat lying, supergene concentrations of rare earths present in the weathering profile (saprolite) overlying granitic basement. This mineralisation is similar in style to the ion-adsorption rare earth clay deposits in China and Myanmar, the world’s main supply source of heavy rare earths. Although this type of rare earth deposit is low grade (typically <1500 ppm TREO), low-cost open continuous mining and simple metallurgy potentially make them commercially viable.
Mineral Resources
HRE discovered significant concentrations of rare earths at Cowalinya in drilling of 109 air core holes in 2021. This led to estimating the project’s maiden Mineral Resources of 28 Mt @ 625 ppm TREO at a cut-off grade of 300 ppm TREO-Cerium oxide (CeO2).
HRE followed up this success by drilling an additional 441 air core holes at Cowalinya in 2022. This program broadened the extent of rare earths-rich mineralisation and led to a substantially upgraded estimate of Mineral Resources for the project: 159 Mt @ 870 ppm TREO.
TREO = La2O3+CeO2+Pr6O11+Nd2O3+Sm2O3+Eu2O3+Gd2O3+Tb4O7+Dy2O3+Ho2O3+Er2O3+Tm2O3+Yb2O3+Lu2O3+Y2O3
Magnet REOs = Pr6O11+Nd2O3+Tb4O7+Dy2O3
Reported above a cut-off grade of 400 ppm TREO-CeO2
Importantly, the resource remains open in all lateral directions, and has a very desirable rare earths composition where 28% are the valuable magnet rare earths (Pr, Nd, Tb and Dy) and 23% the strategic heavy rare earths. In addition, the resource is shallow (average 15 m deep), thick (average 15 m), and features very low average concentrations of the radioelements Thorium (15 ppm) and Uranium (5 ppm).
Exploration Target
Drilling in 2022 also allowed a sizeable Exploration Target to be estimated for the project: 280-1390 Mt @ 330-1330 ppm TREO. The total area occupied by Mineral Resources (159 Mt) and Exploration Target (up to 1390 Mt) at Cowalinya is 112 km2, or 45% of HRE’s total land position.
TREO = La2O3+CeO2+Pr6O11+Nd2O3+Sm2O3+
Magnet REOs = Pr6O11+Nd2O3+Tb4O7+Dy2O3
Metallurgical Development
Sizing test work by Perth-based Strategic Metallurgy on saprolite-hosted mineralisation from 13 drill composites from across the Cowalinya resource showed an average of 78.5% of the rare earths are hosted in the fines (-25μm) fraction which comprises 37.2% of the bulk saprolite feed mass. Furthermore, simple recovery of the fines fraction delivers better than a two-fold increase in rare earth grade.
These results enable the design of an upstream process flowsheet for the project that removes gangue from saprolite via simple screening and desliming cyclones.
Diagnostic leaching of the rare earths-containing fines fraction from the same 13 composites with a weak solution of commercially available hydrochloric acid shows both high leachability (>75%) of the magnet rare earths and low consumption (<40 kilograms per tonne of fines) of acid, with an average of 82.9% and 18.1 kg/t respectively for material regarded as potential plant feed.
These diagnostic results justify HRE accelerating its metallurgical test program over the remainder of 2022 to both expand its diagnostic leaching program by another 60 drill composites, and commence a bench-scale program to develop a downstream flowsheet to a Mixed Rare Earth Carbonate (MREC) product which represents the first entry point by clay-hosted projects into the rare earth supply chain. Subject to the success of this program, HRE plans on making MREC samples available to international and domestic refiners to determine marketability.