Received a reply from the company. Copied below.
Thanks for your email and interest in American Rare Earths.
As noted in conclusions/recommendations, extensive refinery testwork is planned to confirm assumptions around the revised flowsheet – the early leaching tests were WHIMS-based and showed a lower leach recovery for Heavy Rare Earths, since that time the concentration work has improved and flowsheet modified. Our consultant(s) [metallurgist and chemical engineer] evaluated the dataset during continued design work and opined the results were an analysis error due to the extreme low concentrations of the heavies in the leach solution. The heavy rare earths are believed to be coming from allanite, as such all the REE will have the same chemical makeup and should behave the same.
I hope that is enough information for you. Please come back to us with anything further.Their reason is "analysis error [in the leach testwork] due to the extreme low concentrations of the heavies in the leach solution". "REE.. should behave the same". So admittedly they pulled the Dy (and Tb) recovery from thin air with no leach result to back that figure up? Might let Andrew Tunks at MEI know to pump up their recovery numbers in their scoping study.. it's only fair game.
This "extreme low concentrations" reason doesn't pass the pub test. The concentration of heavies in these leach solutions are 70x higher than MEI's concentrations in their leaching met testwork - is MEI's data wrong then?? Calcs to back up my statement below. These leach tests were run by ALS in Australia, and would have been assayed using the same ALS methods that MEI use (ME-MS02). Additionally, the low Dy extraction is replicated across 7 different leach tests and is consistent with the other heavy Y. If there was a +/- 100% analytical error, the results would not have repeated so well between tests.
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| ARR | MEI |
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| 1 | Leach Head Grade | TREO (ppm) | 15,105 | 4,439 |
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| 2 | Leach Head Grade | Dy2O3 (ppm) | 189.6 | 41.2 |
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| 3 | Leach % Solids | wt% | 30% | 2% |
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| 4 | Leach Extraction | % | 36% | 51% |
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| 5 | Test Scale | kg slurry (nominal) | 1 | 1 |
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| 6 |
| kg solids | 0.3 | 0.02 |
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| 7 |
| kg liquor | 0.7 | 0.98 |
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| 8 |
| L liquor (assume SG=1) | 0.7 | 0.98 |
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| 9 |
| Dy IN solids - mg (grade x solids in) | 56.8823 | 0.8245 |
|---|
| 10 |
| Dy OUT liquor - mg (Dy IN x extraction) | 20.478 | 0.420 |
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| 11 |
| Dy liquor concentration (mg/L) | 29.254 | 0.429 |
|---|
| 12 |
| ALS ME-MS02 Dy detection limit (mg/L) | 0.001 | 0.001 |
|---|
There is no way the company backtracks on this scoping study, but I will be expecting the PFS to look very different when these pie in the sky recovery assumptions are no longer acceptable.
(20min delay)