Answer: marcasites

AnswerCrossword Clue
marcasitesA bronze-yellow mineral consisting of iron disulfide but differing from pyrite in typically forming aggregates of tabular crystals
marcasitesA semiprecious stone consisting of pyrite
marcasitesA piece of polished steel or a similar metal cut as a gem
marcasitesMARCASITE, sulphide of iron in orthorhombic crystals