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The underground project spans two pits, Central and North, with five portals planned across the sites. Portals are the entry points from the surface into the underground mine.
The Central pit portal blasts in October follow the restart of underground development at North pit in September. At North pit, the decline is planned to reach 850m below the surface, while the decline at Central pit will extend to a depth of 540m.
First ore from underground stoping, the method of extracting ore from underground, is expected in Q4 FY27. Stoping production at Central pit is planned for Q4 FY27, with North pit to follow in Q4 FY28.
From FY28, Mt Marion will operate as a combined open-pit and underground mine, with underground ore expected to supplement up to 40% of the processing feed.