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Colin Hay

St Barbara’s (ASX: SBM) “Simberi Expansion Concept Study” has highlighted the potential of the Papua New Guinea gold mine’s 10 Year Plus Mine Plan Outlook.

The Concept Study considered six different cases comprising two flowsheet options with three different processing rates.

Investment in the 3.7 Mtpa options provide the most compelling development pathway – lifting Simberi’s production from its current range of 70-75 koz across FY25 to FY27 to an average of 230 koz from FY28 at an AISC in the range of US$1,000 to US$1,200/oz.

“The Concept Study provides a strong case for St Barbara to push forward with the larger 3.7 Mtpa throughput options at Simberi. We now have a road map we can pursue that can take us to increased, more profitable production at Simberi into the mid-2030s,” Managing Director and CEO Andrew Strelein said.

“Our strategy with Simberi has been to extend the production of oxides into 2026, which we are now executing; increase the Sulphide Resource and Reserve through extension drilling, which is underway; and revisit the sulphide expansion development plan. The Concept study is a major milestone in progressing that development plan and we are excited about the potential of this project.”

“Given the opportunity at Simberi and the unreasonable treatment of the company by Nova Scotia Department of Environment and Climate Change, the company does not intend to allocate significant growth capital to the company’s Nova Scotia Projects while advancing Simberi. We can review that position if there is change there.”

The Concept Study

The Concept Study considered six different cases comprising two flowsheet options with three different processing rates (2.0 Mtpa, 3.0 Mtpa and 3.7 Mtpa). The two flowsheet options were as follows:

  • production of a gold concentrate for sale (referred to as the Saleable Concentrate flowsheet); and
  • production of gold doré from ultrafine grinding (UFG) and cyanide leaching of the concentrate (referred to as the Concentrate UFG / Cyanidation flowsheet).

Mine planning work and compilation of the study report was undertaken by Australian Mining Consultants Pty Ltd (AMC). The process options work was undertaken by Chemech Consulting (Chemech) and the capital estimation by Professional Cost Consultants (PCC). The work is more fully discussed later in this release.

The Concept Study has demonstrated that there is a strong case for St Barbara to invest in higher throughput options under both flowsheet options. Furthermore, the Concept Study revealed that that the Concentrate UFG / Cyanidation flowsheet has potential to improve investment returns over the Saleable Concentrate flowsheet options for any given throughput rate.

The Simberi 10 Year Plus Mine Plan Outlook assumes the 3.7Mtpa Saleable Concentrate flowsheet. However, the choice of flowsheet will be reviewed when parameters for the Concentrate UFG / Cyanidation flowsheet are confirmed by the metallurgical testwork programme already underway.

The company has recently been successful in extending the operating mine plan with the existing Carbon-In Leach (CIL) flowsheet until beyond FY28 if necessary. This has been possible due to a combination of ongoing mine design work and adoption of a new material classification and modelling approach developed for St Barbara by Stratum AI.

Although the mine life possible with the existing CIL flowsheet extends, if necessary, beyond FY28 this Simberi 10 Year Plus Mine Plan Outlook anticipates the transition to production of a saleable concentrate in H1 of FY28 with the mine plan ramping up in parallel with the construction works. Accordingly, the execution of the existing CIL flowsheet mine plan is the same through FY25 and FY26 but from the start of FY27 the mine plan diverges ahead of the transition.

This gold production and AISC profile has been extracted from the Concept Study and the detailed mine plan for CIL operations over FY25 and FY26 with the relative contributions from Pigiput, Sorowar, Pigibo and the remainder of the open pit sources.

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