Leach Tests Confirm Positive Recovery From Stromberg HREE Clays
Perth, Mar 5, 2012 AEST (ABN Newswire) - TUC Resources Limited (
ASX:TUC) is pleased to report superior recovery grades from initial leach tests on Heavy Rare Earth (HREE**) rich clays from the Stromberg Prospect.
Highlights
Ongoing metallurgical and mineralogical test work on mineralisation from TUC's Stromberg HREE Prospect yields positive results:
- Up to 77% HREE recovery by direct leach of unrefined material with sulphuric acid, and recovery of up to 62% with hydrochloric acid, but with much lower acid consumption.
- Leaching of the HREE's directly into solution potentially results in a more direct route to a REE carbonate material, which will allow TUC to generate more competitively valued product, when compared to other concentration methods.
- Mineralogy studies show the presence of very fine Xenotime in all clay fractions. Xenotime is a highly sought after mineral from a HREE perspective and the fine fraction is more likely to be susceptible to direct leaching methods.
Metallurgical Update
Four composite samples at varying grades were selected from across the Stromberg HREE deposit for preliminary metallurgical testing. Leach testing of the samples using varying concentrations of acids has revealed a number of interesting clues as to recovery expectations for Stromberg. Up to 77% recovery of the REE was achieved with direct leaching by sulphuric acid (1 part acid to two parts water). Grade recovery curves are flat highlighting the potential for a greater tonnage of treatable material; even lower grade mineralisation (0.1%-0.2% Total Rare Earth Oxides (TREO*)) returned a 69% recovery.
Although on the most promising test, acid consumption rates are relatively elevated (at this stage ~0.4 tonnes per tonne of material, no recycling accounted for), a still impressive yield of ~64% recovery was achieved with a much lower consumption of hydrochloric acid. This suggests that use of a different strength reagent may further improve recovery rates and may yet decrease reagent consumption and costs.
Leaching of the HREE directly into solution results in a more direct route to a HREE carbonate material, which will allow TUC to generate more competitively valued product, when compared to other concentration methods.
The leach tests also extracted 85% of uranium mineralisation, possibly creating a secondary revenue stream for the project, whilst simultaneously serving to boost marketability and exportability of any future HREE product.
Furthermore, all of the deleterious element Thorium was left behind in the residues, significantly upgrading the quality/marketability of the final product.
It is significant to note that, whilst these results remain quite impressive, they are still at a first pass testing stage, and evidence exists that the process could be improved. The next stage of testing has commenced and involves experiments with different chemicals (sodium acetate, sodium carbonate, and ammonium sulphate) and addition of some minor physical processing work prior to leach tests to see if the results can be enhanced. The gangue material is largely composed of inert silica with low calcium contents, which suggests that lower reagent consumption can be achieved.
Mineralogical Update
Mineralogy studies show the presence of very fine Xenotime in the clay fractions of four prospect wide composite samples taken at grades between 0.1% TREO and 1% TREO. Xenotime is a highly sought after mineral from a HREE processing perspective.
The float (fine) material was found to consist of predominantly kaolin clay, with lesser quartz and iron oxides. Very fine grained (~ 5 µ, or less commonly 10 µ) Xenotime minerals were detected as discrete particles or attached to the Kaolin clay. The very fine grainsize of the Xenotime may make the ore more susceptible to direct attack by the acid or other leaching processes which will aid in recovery.
Implications
Ongoing interpretation of geological sections at Stromberg, has revealed the presence of multiple enriching weathering events which have likely contributed to several 'zones' of mineralisation. The large portion of HREE are thought to be hosted within a clay dominant horizon, which may then host localised discrete Xenotime lenses. (See Figure 3 for a geological interpretation of the weathering events and mineralised zones at Stromberg). This interpretation, in combination with the continued flow of encouraging metallurgical and mineralogical results has decidedly positive implications for efficient, expedient, and low-cost mineral processing operations at Stromberg.
*Total Rare Earth Oxides (TREO's) have been calculated by addition of common oxide values for Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Tm, Yb, Y. REO values have been calculated from rare earth element (REE) ppm grades after analysis by lithium-metaborate fusion and ICPMS , where possible, or by HF/multi acid digest and ICPMS. The total REO is calculated as the sum of all REE as REE2O3, with the exception of Ce, Pr and Tb; which are calculated as CeO2, Pr6O11, and Tb4O7 respectively, in accordance with geochemical conventions.
**Heavy Rare Earth Elements HREE's = Dy, Er, Ho, Lu, Tb, Tm, Yb, Y;
Medium Rare Earth Elements MREE's = Gd, Eu, Sm;
Light Rare Earths LREE's Ce, La, Pr, Nd.
Contact
TUC Resources Limited
Ian Bamborough, Managing Director
T: +61-8-8947-0944
E: ibamborough@tucresources.com.au
WWW: www.tucresources.com.au/
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