Feb 20 (Reuters) - Rare earths producer MP Materials ( MP )

said on Wednesday its fourth-quarter loss widened due in

part to higher production costs for the refining of the

minerals.

The Las Vegas-based company reported a net loss for the

period ended December 31 of $22.3 million, or 14 cents per

share, compared to a net loss of $16.3 million, or 9 cents per

share, in the year-ago quarter.