St Barbara Limited ('St Barbara' or the 'Company') (ASX: SBM) is pleased to announce that results of the current testwork program have allowed the early selection of the Saleable Concentrate Flowsheet option for the Simberi Sulphides Expansion, three months ahead of schedule.
The testwork program has also confirmed that the Sorowar ore has significantly lower competency than previous test results, reducing the average life of mine (LOM) ore competency by 20% thereby reducing the crushing and grinding energy requirements.
Managing Director and CEO Andrew Strelein said 'We are excited by the improvements in the recoveries-toconcentrate and overall recovery being achieved in the flotation testwork we have completed to date. The results have allowed us to take an early decision in favour of the Saleable Concentrate Flowsheet, three months earlier than anticipated.' 'The confirmation of our expectations of the consistency and competency of the Sorowar ore's crushing and grinding characteristics with those of Simberi's other ore zones is a breakthrough. The simplification of the ROM pad and crushing circuit was just the first 'value-unlock' that we anticipate from this important clarification of the Sorowar ore properties. The testwork program is revealing enormous potential for flexibility in the sequencing of the open pits, pit backfill strategies to reduce waste dump construction and potential savings in waste haulage costs as well as dramatically simplifying mine closure and reclamation planning.' 'The demonstrated benefit of the flotation circuit design optimisation and the value we have unlocked from confirming Sorowar's ore properties have already delivered a return on our investment in FY24's comprehensive metallurgical drilling and testwork campaign.' The Company is well funded to complete the next phases of work and beyond, including the investment in PreExpansion Growth Capital. This sets us up to deliver the clearest possible scope of work for the final investment decision anticipated in Q2 December FY26. Current oxide production at Simberi is expected to operate at around breakeven cashflow for FY25, inclusive of funding a significant Sustaining Capital investment. Accordingly, the FY25 investment in Pre-Expansion Growth Capital is being funded from the Company's balance sheet. Operating cashflow and AISC are anticipated to improve in FY26 and FY27 with lower Sustaining Capital investment and further improvements in mine fleet and process plant performance. These will be some of the benefits of the investments being made in FY25.
Metallurgical Testwork Update
Comminution Property Testwork The current comminution testwork results for Sorowar ore has revealed significantly lower (40%) competency (DWi and Axb) than historical results, indicating lower coarse particle breakage (SAG milling) energy requirements. The DWi value of 2.7kWh/m3 for the current LOM ore blend is 20% lower than that used in previous studies and the LOM Axb value of 86 classifies the ore as 'extremely soft' with respect to competency. Bond Ball Mill Work index (BWi) values are consistent with previous test results indicating that the fine grinding (ball mill) requirements will be similar. The average BWi value for the LOM blend is 16.4 kWh/t, indicating that the ore is hard in the finer size fractions. The abrasion index values are low
Selected Flowsheet
With comminution testwork now complete, preliminary comminution modelling of the LOM ore blend has confirmed the crushing and grinding circuit configuration and major equipment sizing. Crushing will be via a new MMD 625 Series Sizer. This has recently been purchased. The existing 2.6 MW SAG mill is being retained and will be coupled with a new 5 MW ball mill. The ball mill size is based on a preliminary grind size selection of 106 -microm as it showed an improved recovery, grade and concentrate mass pull over the previously selected grind size of 150 -microm. Further grind size versus recovery testwork is planned and an economic assessment of the final optimum grind size will be made when testwork is complete. The circuit design that includes retention of the existing SAG mill will minimise downtime related to tie-in of the new circuit. The current Carbon-in-Leach plant has parallel, rather than sequential, SAG and ball milling circuits allowing the SAG mill to continue operating while the new ball mill is installed. The circuit design will also be configured to allow rapid changeover between oxide / transitional ore processing (direct leach) and sulphide ores (flotation and leach). Cyclone overflow from the new ball mill circuit will be pumped to a new flotation circuit. Flotation circuit configuration and equipment selection will reflect the testwork objectives of: 1. Maximising flotation gold recovery as the tailings leach recoveries are relatively low
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Competent Persons Statement
The information in this report that relates to Exploration Results is based on information compiled by Dr Roger Mustard, who is a Member of The Australasian Institute of Mining and Metallurgy. Dr Mustard is a full-time employee of St Barbara and has sufficient experience relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the 'Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves'. Dr Mustard consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.
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