Assays from Waste Tip Return Grades up to 11.35 g/t
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Alba Mineral Resources plc (AIM: ALBA) is pleased to provide an update regarding the Clogau-St David’s Gold Mine (“Clogau” or the “Mine”), where assay results from a Phase 2 sampling programme undertaken at the historic Waste Tip have returned gold grades of up to 11.35 g/t.
· Gold grades of up to 11.35 g/t from samples of the five pits dug in January 2022.
o Whole-sample analysis averages up to 3.50 g/t, similar to Phase 1 results.
o Average gold grades returned for the fine fractions (<1mm) are up to 2.13 g/t.
· Further size fraction analysis has highlighted how gold is concentrated in the finest material (<1 mm) extracted from the dump.
· 107 kg of concentrate produced in the Company’s pilot processing plant from 8.76 tonnes of sub 20mm fines material collected in January 2022.
o The panning of one sample of the <20mm fraction reveals a material amount of visible gold.
· Next steps
o Upgrade the 107 kg of concentrate, assess the economic potential of processing this section of the Waste Tip and develop an outline Mining Plan.
o Evaluate taking a further bulk sample from lower down within the Waste Tip to access potentially higher-grade material.
Alba’s Executive Chairman, George Frangeskides, commented:
“With gold grades of up to 11.35 g/t, in tandem with a successful initial bulk sampling programme, we hope to fast-track the start of low-cost production from the Waste Tip at this historic gold mine. Additionally, given the fine nature of the material that has the potential to filter downwards, we are exploring options to take a second bulk sample from the lower reaches of the Waste Tip that could further strengthen the Project’s economics.”
Further to the RNS dated 10 January 2022, Alba has received the assay results from its Phase 2 sampling programme at the Waste Tip at the Clogau-St David’s Gold Mine (“Clogau” or the “Mine”) and, through its pilot processing plant, has also produced 107 kg of concentrate from an 8.76 tonne bulk sample collected from the Waste Tip. The panning of one sample of the <20mm fraction derived from Pit 1 has confirmed a material quantity of visible gold (Figure 1).
Figure 1: First gold pan of <20mm sample from Pit 1 (March 2022)
The Waste Tip at Clogau, which covers 2,833 m², comprises ore rock mined but discarded and not processed for its gold content during historical mining. Having completed an initial programme, Phase 1, at the Waste Tip in June 2021, which returned significant gold grades of up to 9.89 g/t, the Company commenced a Phase 2 pitting and sampling programme in January 2022. This was focused on a more targeted area within the Waste Tip (Figure 2) to assess grades and tonnages more accurately, so that Alba can proceed towards a formal decision on the commercial exploitation of the Waste Tip, whether in part or as a whole.
The Waste Tip is close to Alba’s pilot processing plant and could be mined at low cost, adding another route to near-term gold production at Clogau. Current estimations of the higher-grade portion of the dump indicate an in-situ tonnage of approximately 11,000 tonnes, of which up to 4,000 tonnes of fine material (<20mm) could be available for processing for gold.
Figure 2: Location of zone selected for Phase 2 pitting (red). Waste Tip boundary shown in white.
Five pits were dug by excavator and the material excavated from each pit was screened on-site to a size fraction of less than 20mm. From this finer material (~1-2 tonnes of material per pit), a sample of around 60kg was taken per pit and submitted to an independent laboratory for assay.
Initial processing of the samples was delayed due to Covid-related staffing issues at the independent laboratory. Once processing was able to commence, for each 60kg sample, half of the material from each pit (Branch A) was crushed and then split into five samples which were assayed separately in order to give a representative average of the gold deportment for the whole sample. This is termed the ‘whole-sample’ assay grade.
The other half of the sample (Branch B) was screened to three size fractions: coarse (20mm-5mm), medium (5m-1mm), and fine (<1mm). Each size fraction was then assayed separately for further size fraction analysis.
Table 1: Whole-Sample Assay Grades from Individual Samples (Branch A)
Table 1 shows the whole-sample assay results for individual samples (Branch A), with grades above 1 g/t highlighted. Table 1 shows that gold grades of up to 11.35 g/t were returned from Pit 1, exceeding the highest grades seen to date in individual samples from the Waste Tip in Phase 1 sampling.
Figure 3: View of the highest-grade Pit 1 with accompanying whole-sample average, highest and lowest gold grades returned.
Table 2 demonstrates further size fraction analysis which confirms the observations of Phase 1 sampling, in that gold is concentrated in the fine fraction of material extracted from the waste dump, with averages reaching up to 2.13 g/t. The highest average grade for the medium (1mm-5mm) and coarse (5mm-20mm) size fractions are 1.03 g/t and 0.56 g/t, respectively.
These results give representative mill head grades of 0.27 to 3.5 g/t (whole-sample average grades) for immediate processing from these five sites.
Table 2 shows a summary of the average gold grades for the three size fractions (Branch B), whole-sample average gold grades (Branch A) and representative mill head grades (Branch A + B) for each pit.
Table 2: Average Gold Assay Results per Size Fraction (Branch B)
The variation in average gold grades between branch A and B is consistent with the nuggety nature of the gold. This supports the decision of Alba to install a simple gravity processing plant to capture the majority of the gold.
Table 3: Comparison of Average Mill Head Grades from Phases 1 and 2
Table 3 shows that weighted average head grades for each Pit from Phase 2 are very close in value to the grades returned for each pit from Phase 1 sampling in June 2021. This further increases the confidence in the average gold grades consistently returned from pits in the Waste Tip at Clogau.
Measurements show that the sub-20mm size fraction constitutes an average of 36% of the total mass of the dump. This material has the potential to be mined at low cost in Alba’s on-site processing plant once a plan has been designed and submitted to excavate and process the fines from this section of the Waste Tip.
Processing of Bulk Sample from Waste Tip
Taking large bulk samples has allowed Alba to representatively quantify average gold grades for each pit, helping to counteract the variability between individual samples due to the nuggety nature of the gold within the Waste Tip at the Mine.
Alba has completed the processing of the 8.76 tonnes of excavated fine (<20mm) material from these five pits, which material had been stockpiled at the mine site. The purpose of processing is both to extract the gold content from the bulk sample and to further assess the economic potential of processing the higher-grade section of the dump.
The 107 kg of concentrate produced from the processing of the 8.76 tonne bulk sample will now be processed on-site over a Wilfley shaking table for further gravimetric concentration of the gold. This will enable the Company to further assess the economic potential of processing the section of the Waste Tip covered by this Phase 2 exercise. A positive outcome from that assessment will lead to the development of an outline Mining Plan which will feed into a formal planning application to exploit that section of the Waste Tip.
The Company is also evaluating the taking of an additional bulk sample from a zone lower down within the Waste Tip in order to access further potentially higher-grade material. Given the higher-grade material in the Waste Tip has been shown to reside within the fine fraction, it is possible that a greater proportion of this material will have migrated over the decades to the lower reaches of the Waste Tip (see Figure 4).
Figure 4. Aerial view of a section of the Waste Tip showing the maximum depth extent (approximately 10/ metres)
Update on Water Discharge Application
As previously reported, the Company has been progressing work on a set of detailed submissions seeking the further consideration by the authorities of the Company’s dewatering application for the necessary permits to allow treated mine water from the Llechfraith Shaft to discharge to the River Cwm-Llechen.
Following further discussions with the competent regulator, the Company and its retained hydrogeological, geochemical and ecological consultants have generated further data and analysis which have been included in an extensive report which has been submitted to the regulator for its consideration and ultimate decision.
This announcement contains inside information for the purposes of the UK Market Abuse Regulation and the Directors of the Company are responsible for the release of this announcement.
For further information, please visit www.albamineralresources.com or contact:
Alba Mineral Resources plc
George Frangeskides, Executive Chairman
+44 20 3950 0725
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