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Jan 22 (Reuters) - Australia's Lynas Rare Earths (LYC) on Monday reported a sharp drop in second-quarter revenue reflecting a plunge in underlying prices coupled while a planned shutdown of its Malaysian operations which hurt output.

The world's largest producer of rare earths outside China said sales revenue fell by 51.7% to A$112.5 million ($74.06 million) in the three months to Dec. 31, 2023 compared with A$232.7 million a year ago.

Underlying rare earth prices sank during the quarter on the back of easing demand from green energy firms along with rising supply from top producer China.

Rare-earth miners have struggled with the supply-chain dominance of China, the world's largest producer and processor, and a history of extreme price volatility, most recently at the start of 2022.

The world's largest producer of rare earths outside China shut down Malaysian operations in mid-November, except for a mixed rare earth carbonate processing plant in this quarter to upgrade downstream operations.

The miner's neodymium and praseodymium (NdPr) output for the quarter ended Dec. 31 came in at 901 rare earth oxide tonnes (REOt), compared with 1,508 tonnes a year earlier.

The drop in sales came even as Lynas raked in an average selling price of A$28.70 per kilogram (kg) for its product range, compared with A$58.40 per kg recorded last year. ($1 = 1.5191 Australian dollars)