Nov 7 (Reuters) - U.S. rare earths miner and processor MP Materials Corp

on Thursday reported a smaller-than-expected loss in the third quarter, helped by higher production and sales volumes of the strategic materials.

MP processes rock it extracts from its Mountain Pass mine in California into rare earths concentrate that is shipped to China for refining.

The company sold 9,729 metric tons of that concentrate during the quarter, 6% higher than the year-ago period.

The growth in sales was driven by higher production volumes, reflecting higher mineral recoveries and operational efficiencies, the company said.

However, realized prices of rare earth concentrates declined 23% in the quarter due to ongoing soft pricing environment for rare earth products.

MP Materials produced 478 tons of neodymium and praseodymium (NdPr) — the two most in-demand rare earths — during the quarter, with 404 tons sold. Sales nearly tripled sequentially.

"Despite continued weak market pricing, increased NdPr sales volumes drove a return to year-over-year revenue growth," said CEO Jim Litinsky, who is also the largest shareholder of the company with an 11.2% stake.

Cost of sales rose over 150% in the quarter, but were partially offset by a reduction of an inventory reserve of $2.7 million recorded in the quarter.

Excluding one-time items, MP posted a loss of 12 cents per share, compared with analysts' expectations of a loss of 13 cents per share, according to data compiled by LSEG.

(Reporting by Mrinalika Roy in Bengaluru; editing by Alan Barona)

((mailto:mrinalika.roy@thomsonreuters.com))