Mt Carbine Development
At the Mt Carbine site, in addition to the current tailings retreatment project and the Mt Carbine Quarries business, EQR is pursuing further expansion and developments, namely in relation to a sorter plant expansion for the XRT Sorter Technology and developing an underground mine utilising an historic decline. EQR is completing the required permitting relating to the increased processing capacities of each operation with the estimated timeline set out in the graphic below.
MT CARBINE HARD ROCK RESOURCE
EQR is re-defining the Mt Carbine underground resource and has initiated a trade-off study on the mining method, focused on the zones of high-grade mineralisation within the larger world-class global resource at the Mt Carbine tungsten deposit (46Mt @ 0.14% WO3).
The Company is evaluating the underground development potential for a narrow high-grade mine to extract ‘King-Vein’ style mineralisation which is defined using a minimum mining width and grade of 2m>0.2% WO3. This allows for less dilution when compared to the previously defined sub-level caving methodology proposed by historical owners in 1985 for which a 430m decline was constructed at the time. Upon relogging the historical core and assaying of certain sections for reinterpretation, the data is consistent with most of the mineralisation being contained in these high-grade veins, leading to the potential of a much higher-grade resource enclosed in less tonnage.
With this information and understanding, EQR is now investigating the cost of re-opening the 430m decline to complete underground sampling. Once completed, the company will have an understanding of how best to develop the remaining hard rock resource to maximise the remaining value. Detailed development plans will be compiled once the next round of relevant test work is completed. EQR aims to have the hard rock resource operating by the end of 2022.
The 12 million tonne low grade/mineralised stockpile at Mt Carbine is set to be the primary feed source over the coming years for the XRT Sorter and the gravity plant located at Mt Carbine. Optical ore sorting was used at Mt Carbine between 1973 and 1986 where the white quartz was removed from the associated rock. At that time, it was believed that the tungsten was found only in the quartz. With advances in technology, it has been revealed that the scheelite mineralisation is mainly found in the quartz, however, the wolframite mineralisation (the other tungsten bearing mineralisation) is found in the quartz and associated host rock. This means that while the historic mining operations targeted the scheelite, they missed a significant amount of the wolframite in the ore.
There have also been major advances in the type and efficiency of ore sorters since they were last used at Mt Carbine. During late 2010, the Company (formerly known as Carbine Tungsten Limited) carried out trials using an XRT sorter on bulk samples taken from the low-grade stockpile left untreated by the previous mining operation. The results were positive and have led to bulk testing of the stockpile with the latest XRT Sorter technology which with first samples being processed in August 2020.
The Company is now completing a bulk test work program using a TOMRA XRT Sorter on the Low-Grade Stockpile and the other waste rock stockpiles on site to determine upgradeability and viability of the material. Early results (as announced to ASX on 7 September 2020) have shown an excellent early upgrade in the material tested. Further optimisation and test work are needed across the stockpiles before moving to a continuous production scenario.
Once the current bulk testing campaign is completed, the pilot XRT Sorter currently setup on site will be operated on a full-time production basis. The Company is in the process of completing the required environmental amendments to allow the operation to process 300,000tpa and eventually 1Mtpa targeted for Q2 2022. Once the bulk test work is completed, a feasibility study will be completed for the design of the 1Mtpa operation.
TAILINGS OPERATION DEVELOPMENT
The tailings operation has been developed into an operational cash generating asset during 2020. Going forward, the development plan for the Mt Carbine activity hub is to focus on the higher grade mineralised stockpiles. Processing capacity limitations mean that the mineralised stockpiles, as opposed to the tailings material, will be the primary source of feed for the gravity plant. As and when additional or supplementary feed is required, the tailings material will be processed to recover the remaining quantities of tungsten mineralisation.