59a) One of the major Iranian Gnostic religions, originating in Sassanid Persia, that thrived between the third and seventh centuries (13) m-n- - - a-a-ism I think the answer is manichaeism but it doesn't fit in.
55d) A large neck ring usually made from strands of metal twisted together (4) -o- - The last letter here is the fifth of the previous answer. Thanks in advance. I've often wondered why this crossword never gets many requests for answers, it is one of the hardest ones at times.