Duritanium (or duratanium) is the Star Trek equivalent of adamantium -- a super-hard, super-durable metal that is used for hull plating and other structures that require a smerpload of reinforcement. It first appeared in the Voyager series, but was also mentioned in the Star Trek prequel, Enterprise. No real information is given, other than the facts that it is traded on the open market, it can be used to reinforce starship hulls, and can be used (and thus, presumably molded/shaped) by a starship without returning to port.