MELBOURNE (Reuters) -Australian miner Lynas posted a slump in third-quarter sales revenue on Wednesday, missing analyst expectations on the back of a plunge in prices for rare earths, while it flagged higher costs at a project in Western Australia. Prices of rare earths were fairly weak during the third quarter, as increased production in China, the top producer, and slower-than-expected demand growth recovery remained a drag. "The market continues to be less than kind to us and to anybody else in rare earths sector," CEO Amanda Lacaze told analysts on a quarterly call, noting a ...