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May 2 (Reuters) - Rare earths miner MP Materials MP.N reported wider-than-expected loss in first quarter on Thursday, hurt by lower concentrate sales and weak prices of the strategic materials.

MP processes rock it extracts from its Mountain Pass mine in California into rare earths concentrate. It is the second-biggest producer of rare earths outside China after Australia's Lynas Rare Earths (LYC) and produces about 15% of the rare earth content consumed annually.

The strategic materials are critical to the energy transition and the future of the automotive industry. The United States is investing billions of dollars to shore up access to rare earths.

However, slowdown in EV demand, along with economic and geopolitical uncertainties have weighed on prices.

The miner has struggled with falling prices for the strategic minerals and, in February, had flagged a mid-teens sequential decline in first-quarter realized concentrate pricing.

The company sold 9,332 metric tons of that concentrate during the quarter, about 9% lower than the year-ago period.

CEO James Litinsky said the company experienced "difficult pricing environment" in the quarter.

The company reported adjusted loss of 4 cents per share, compared with analysts' expectations of a loss of 2 cents per share.