mar·ca·site 
(märkə-sīt′, -zīt′)
(märkə-sīt′, -zīt′)n.
1. A mineral with the same composition as pyrite, FeS2, but differing in crystal structure. Also called white iron pyrites.
2. An ornament of pyrite, polished steel, or white metal.
[Middle English, from Medieval Latin marcasīta, from Arabic marqašīṯā, from Aramaic marqəšitā, from Akkadian marḫašu, from marḫaši, ancient region in the eastern Iranian plateau.]
mar′ca·siti·cal (-sĭtĭ-kəl) adj.