Excellent initial metallurgical results from Silver Tailings Project at Elizabeth Hill
Potential for economic recovery and for the project to be a significant source of income
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Alien Metals Ltd (LSE AIM:UFO), a minerals exploration and development company, is pleased to provide an update regarding the Company’s exclusivity agreement over the Elizabeth Hills Silver Tailings Project (the “Project”) at Elizabeth Hill, Western Australia, as announced on 10 March 2021.
Initial results from 6 samples that have been subject to test leaching by ALS Perth are very encouraging and have returned high levels of silver recovery.
Alien has extended the exclusivity period with the Project owner for a further 45 days to factor in the backlog of work from laboratories in Perth due to the current high workloads they are experiencing. This extension will allow Alien to undertaken further assessment over the potential retreatment and recovery of the silver tailings as discussions continue regarding the potential acquisition of the Project.
Highlights
· Excellent initial recovery results from metallurgical testing
· Maximum of 95.2% silver recovery, with an average recovery of 91.9 % silver from 6 samples
· Head grade comparison highly repeatable
· Recent sampling of the tailings undertaken by Alien and announced on 10 March 2021 returned very encouraging results:
o 84 samples were taken from 21 locations, with silver grades up to 1,270 g/t (38 oz/t)
o The samples returned an average grade of 472 g/t Ag (13.3 oz/tAg)
· Extension of exclusivity period granted for a further 45 days
Bill Brodie Good, CEO & Technical Director of Alien Metals, commented:
“We have been aware of the potential of the historic silver tailings at Elizabeth Hill for some time. Knowing that the Elizabeth Hill silver mine’s historic operations were somewhat inefficient and being a very high-grade project with abundant native silver in the orebody we felt that, despite previous reprocessing activities, there is likely significant value remaining in the silver tailings.
“These initial metallurgical results are really encouraging and have given the management confidence that, with further test work, the silver tailings hold potential for economic recovery. With the continued strength in the silver price, currently around $28 USD/Oz, we see potential for the project to be a significant source of income.”
Figure 1: Location of Elizabeth Hill Silver Project, Western Australia
The purpose of this initial metallurgical test work was to determine the proportion of the silver content that is amenable to leaching, with the results assisting in the planning of a more formal test work campaign.
The six samples were each riffle split to extract four portions of 50 grams for analysis and leach testing. Three portions were used for triplicate head analyses of each sample. The fourth portion was subject to an intensive cyanide leach to determine cyanide soluble silver. The leach procedure involved two Leachwell assay tablets and 24 hours leach time. The leach solutions and solid residues were then analysed for silver so that percentage silver dissolution and built-up head analyses could be calculated for each sample.
Including the built-up head there were effectively four analyses of total silver for each sample. There was some scatter between the four analyses; this is to be expected due to the “nugget effect” resulting from the presence of coarse silver particles in the samples. However, the degree of scatter was modest, indicating that there were no large nuggets of silver present. The laboratory commented that the ‘reasonable reproducibility of the silver head assays (i.e., x 3 for each sample) and the good silver head balance, suggests the silver is probably present as finer material, which is encouraging from a processing aspect as it means the tailings appear homogenous and suitably ground to date.
The average silver recovery to solution was 91.7%, whilst the highest and lowest recoveries were 95.2% and 88.0% respectively. These results indicate that silver recovery by leaching may be a viable processing method.
For the full table of results see Table 1 in the Appendix.
The Company is working on follow-up metallurgical test work that will establish a cost-effective means of exploiting this tailings resource. Investigations could cover the following:
1. Investigate the applicability of a non-cyanide leach route – e.g., Clean Metals Thiosulfate leach, or acidic thiourea.
2. Investigate cyanide leaching conditions – grind, cyanide strength, leach time, temperature, and effect of other reagents (lead nitrate, oxygen, etc.) on cyanidation.
3. Investigate alternatives for silver recovery from solution to produce a saleable product, e.g., zinc cementation, sulfur dioxide precipitation, resin adsorption then elution and electrowinning, silver sulfide precipitation.
History of the tailings
Located within the Company’s mining lease ML47/342 there remains the partly retreated tailings from the original silver mine operations at Elizabeth Hill. This is currently subleased from Alien by Wombat Resources Pty Ltd (Wombat).
Alien’s preliminary assessment indicates that there remains about 16,000 tons of silver tailings on site, based on tonnage of ore extracted from the mine however further work will be undertaken during the exclusivity period to confirm available tailings for reprocessing.
Historic reports refer to grades above 1,000 g/t (33oz/t) silver in the original tailings due to inefficient processing practices of the ore during historic mining, Ref Independent Technical Assessment Report on the Elizabeth Hill Project, Agricola Mining Consultants, June 2018.
Historically some reprocessing of the silver tailings was undertaken, however limited information exists on processing recoverability.
