My diamond broker has mine to resell to a buyer. Many people sell them back to stores or to a pawn shop. You will usually get something like 30% of the appraised value at a pawn shop.
If your rings are his family heirloom you should give them back though. Regardless I'd wait until after the divorce so he can't claim you sold rings that he should have had. Some XHs are asssholes and will try to get the rings back. Sorry you're dealing with this.