Charles & Colvard (Nasdaq: CTHR) , a producer of the artificial jewel material known as moissanite, is looking for a new chairman and chief executive officer.

Robert Thomas, who held both posts, resigned “effectively immediately,” the company said Monday.

Shares in C&C have plunged to under a dollar after selling as high as $5.27 over the past year. Its 52-week low is 57 cents.

Thomas also gave up his board position but will continue to work with C&C as a consultant, the company added.

C&C posted annual revenues of more than $40 million in 2006 and $27.8 million in 2007 but sales dropped to $3.40 million in the first quarter of this year.

Dennis Reed, president and chief marketing officer at C&C, will run the firm, C&C said.

“While the outlook for the jewelry industry continues to be challenging, we will work diligently to grow the Company,” Reed said in a statement. “In this economic environment, we believe moissanite offers consumers a beautiful, unique, affordable jewel with more fire and brilliance than any other.”

Frederick Russ, a member of the board and an independent director, will take over as board chairman on an interim basis.