The reviewer is a geologist, so take that into account with his interpretation of the metallurgy. He didn't appreciate the CAPEX benefits of heap leaching, or the filtration challenges with clay (only talked about vats but not the huge filter presses with clay plants). Capital intensity is about $30 m USD/mtpa for heap leaching vs $100 m USD/mtpa for clay tank leaching based on multiple recent studies, so that is a significant benefit - one third the CAPEX to heap leach the same throughput.
On the impurity front, he assumed the Sybella granite was 15 wt% Aluminium. Red Metal provided the actual Fe and Al grades of their granite in their announcement, a quick read and he would have seen the Al grade is only 4 wt% for Sybella granite. It is also unfair to pick on RDM for impurities when no other REE clay explorer has released their impurity extraction rates or impurity head grades... Basic chemistry tells you Al
3+ and Fe
2+ are both soluble at pH 4, so even pH 4 leaching can have significant Fe and Al extraction
if the Fe/Al mineralogy supports it.Theoretical Al solubility at pH 4 ambient temperature = ~270 mg/L, Fe(II) solubility at pH 4 > 50 g/L.
Finally, RDM have only done one round of sighter leach testing. MEI (and VMM) has had multiple years of met testing with their project's predecessor to build on. Let's give RDM a bit more time to develop their metallurgy for what is a completely new REE deposit style which will require a unique metallurgical approach. I see in their quarterly the round 2 leach results as well as impurity removal trials are well under way and to be reported this quarter.
If RDM can't make a MREC product that is on par with MEI's specification (57% TREO & 0.3% Al) with high global recoveries, then I will concede this reviewer is correct on the impurities. But let's give RDM a chance to do the downstream metallurgy first.
