St Barbara (ASX:SBM) lowered its fiscal 2025 production guidance for its Simberi operations in Papua New Guinea after failing to achieve the targeted face positions in two key mining locations, according to a Monday filing with the Australian bourse.

Gold production for the 12 months ending June 30 is forecast at 55,000 to 65,000 ounces, compared with prior guidance of 65,000 ounces to 75,000 ounces last confirmed on Jan. 31. The mining company also revised the all-in sustaining costs guidance to AU$3,900 to AU$4,200 per ounce.

"[W]e were already trending to the low end of guidance after the December 2024 Half Year and therefore this lower average mined grade outlook will now leave us short of achieving our previous annual guidance and so this revision has been necessary," said Chief Executive Andrew Strelein.

For the half-year ending June, the mining company expects to produce 32,500 to 42,500 ounces, compared with the reported output of 22,495 ounces in the six months to December 2024.