marcasite


marcasite

Iron sulfide mineral that forms pale bronze-yellow crystals; the name cockscomb marcasite refers to the shape of a common form of its crystals. Marcasite has the same chemical formula as pyrite (FeS) but a different internal (atomic) structure. It is less stable than pyrite, being easily decomposed, and is much less common.

This entry comes from Encyclopædia Britannica Concise.
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