(Reuters) -Australian miner Lynas posted a slump in third-quarter sales revenue on Wednesday on the back of a plunge in prices for rare earths but signaled a slight recovery in April.

Prices of rare earths were fairly weak during the third quarter, as increased production in China and slower-than-expected demand growth recovery remained a drag.

"Market prices have started to increase in April," the world's largest producer of rare earths outside of China said.

The firm's quarterly sales revenue fell to A$101.2 million ($65.64 million) in the three months to March 31, compared with A$242.8 million a year earlier. It missed a Visible Alpha consensus estimate of A$146.3 million, according to Morgan Stanley.

Lynas raised the budget for its Kalgoorlie facility to A$800 million from A$730 million it projected in October.

The company said its Mt Weld Expansion Project in Western Australia scheduled was on track with construction activities progressing as planned during the quarter.

($1 = 1.5418 Australian dollars)

(Reporting by Rishav Chatterjee and Sherin Sunny in Bengaluru; Editing by Sriraj Kalluvila)