hmm. i think raising the turn isn't a bad play. if he doesn't have the goods then the check to induce a bluff was good, and you can take it down now. if he reraises your turn raise he probably has the flush. if he just calls, then i think there's a good chance your hand is either good, or you'll have outs on the river to fill up.

just calling seems weak, and i think if you c/c the turn then he can probably take the hand away from you on the river, especially if another diamond falls

i really can't bring myself to see folding here as a good play