29 July 2022
[Ed note: we have highlighted only the Nunavut activities below. Read the full release for complete information issued by American West]
July 29, 2022
Ore Sorting Test Work
The straightforward nature of the copper mineralogy and host rocks of the Storm Copper Project indicated that it may be amenable to upgrading through beneficiation processing techniques. The ore sorting test work was completed with partners Steinert Australia at their test facilities in Bibra Lake, Western Australia. The test sample was processed using a full scale STEINERT KSS CLI XT combination sensor sorter.
The test sample was selected from preserved core from drill hole STOR1601D. This drill hole is located within the eastern 4100N Zone of the Storm Copper Project. The selected 4m interval from between 97-101m down hole was composited and included approximately 5.5kg of core material with an average grade of 4m @ 4.16% Cu. The test sample is considered representative of the high-grade copper mineralisation discovered at the Storm Project to date.
The composite sample was crushed to a size fraction of 10-25mm, which is the optimal size range for the full-scale ore sorting equipment. The crushed material was then washed before being processed. A minor fraction of fines was lost (~0.03kg) during crushing.
A combination of X-Ray transmission and 3D laser sensors were used in the sorting algorithms given the expected density contrasts between the ore and waste.
Three distinct products were produced from the test work – a Very High Density material which qualifies as DSO, a High Density material and a Low Density material (Figure 16). The weights of each product were 0.56kg, 0.51kg and 4.4kg respectively. Each of the products was split and samples from each were pulverized and prepared as pressed pellets for analysis.
Metal values were estimated using portable XRF and the results are tabulated below (Table 5). XRF analysis of the pressed pellets is considered an accurate estimate of metal values given the composite and homogenous nature of the pellets.
|
Product |
Cu Grade |
Weight |
Estimated Chalcocite Content (approx.) |
|
Ore Sorter Feed |
4.16% |
5.5kg |
|
|
V. High Density |
53.9% |
0.56kg |
81% |
|
High Density |
10.3% |
0.51kg |
16% |
|
Low Density |
0.3% |
4.4kg |
0.4% |
Table 5: Portable XRF results and ore sorter product details
The grades and yield suggests that the Very High Density product is likely comprised of pure chalcocite (Cu2S) and a small fraction of waste material. This unoptimized grade is superior to many other DSO copper products globally, and is due to the simple, monomineralic nature of the copper mineralisation.
The High Density intermediate product likely represents a portion of the sampled interval where there is fine grained chalcocite that wasn’t liberated with crushing of the 10-25mm fraction. Optimisation of the sorting algorithm to recover the remaining fine-grained chalcocite, followed by further crushing is expected to successfully upgrade this material to DSO grades through simple conventional physical separation. Any fines lost in the original crushing circuit will likely be reprocessed with the intermediate material.
The waste material is comprised of dolomite, with very minor unliberated (likely very fine grained) chalcocite. This is expected to have no acid forming potential.
The ore sorting test work has demonstrated that the typical mineralisation at Storm Copper can successfully be upgraded through a simple process to produce a DSO product. The exceptional grade of the Storm DSO is unique and ranks among the highest-grade copper DSO products globally.
The operational benefits of using ore-sorting processing technology are the low capital and operating costs, low emissions and the lack of tailings and reagents. This, combined with the high-grade and shallow mineralisation, provides the Company with a potential pathway to a very low footprint, low cost and ESG sensitive mining operation.
An extensive diamond drilling program has been designed for 2022 with the aim of defining a maiden copper resource at Storm, and to define new zones of mineralisation through testing of high-priority EM anomalies.
The high-grade 2750N zone will be the first to be drilled and will include infill drilling around historical intersections such as 110m @ 2.45% Cu from surface (drill hole ST97-08) and 56m @ 3.07% Cu from 12.2m (drill hole ST99-19). These two intersections are located approximately 100m apart, and within broader a zone of mineralisation over 300m in strike. The 2750N zone is open in all directions.
A number of high priority EM anomalies that were identified as part of the 2021 survey will also be tested. That survey identified seven shallow and seven deep anomalies that are untested and lie in favorable geological locations. For details of the results of the EM survey, see our ASX Release dated 14 December 2021 Outstanding Growth at Storm Copper.
Two of the shallow EM anomalies close to the 2750N zone are associated with significant copper in soil geochemical anomalies and mapped surface gossans, making them compelling targets for the discovery of further copper sulphides.
The geometry and mostly gentle dips of the modelled deep conductors suggest that they may be related to stratiform type targets, and may be indicative of traditional sedimentary type copper mineralisation at depth. One of these deep anomalies lies immediately to the west of the 4100N zone and is interpreted to project close to surface in that location, and therefore may represent the source of the shallow high-grade mineralisation.
The drilling is now underway and will continue during the September quarter.