A sign adorns the building where Australian miner South32 has their office in Perth, Western Australia, November 19, 2015. REUTERS/David Gray/File Photo

(Reuters) -Australia's South32 reported a 75% surge in full-year profit on Thursday, helped by strong performance at its alumina division and higher commodity prices, but still missed expectations.

Shares of the company declined as much as 2.1% to A$2.85 as of 0010 GMT, while the broader benchmark index was largely unchanged.

The diversified miner's alumina operations benefitted from a 45% rise in prices, which lifted the division's operating earnings by $714 million to $1.08 billion.

The aluminium division also benefitted from higher prices of the metal due to supply constraints and rising costs.

South32 said its underlying earnings for the year ended June 30 came in at $666 million, ahead of $380 million a year ago.

However, it missed the Visible Alpha consensus estimate of $697.7 million, weighed down by a lower contribution from Australia Manganese operations stemming from impacts of Tropical Cyclone Megan.

The company expects production growth of 4% for its Worsley Alumina operations for fiscal 2027, as the refinery returns to maximum output due to the improved availability of bauxite.

South32 also expects its Mozal Aluminium smelter to be placed under care and maintenance in March 2026, while limiting investment in the project.

Earlier this month, South32 flagged a $372 million impairment for the smelter, which the miner said it was preparing to mothball as it may not be able to secure affordable power when its supply agreement ends in 2026.

Analysts at Jefferies said fiscal 2026 shows higher operating costs across most operations.

The Perth-based miner, which separated from BHP Group in 2015, declared a final dividend of 2.6 cents per share, compared to 3.1 cents in the previous year.

It also extended its current capital management by a year to mid-September 2026, with $144 million left to be returned to shareholders.

(Reporting by John Biju and Adwitiya Srivastava in Bengaluru; Editing by Vijay Kishore and Alan Barona)