Cast Iron. A ferrous metal object formed in a mold. It is gray when freshly cast but will oxidize to a dull red as unprotected iron surface rusts in the atmosphere of moist air. In the numismatic and medallic field a small number of plaques and patterns are made of cast iron. The surface of such cast objects are typically grainy with edges of detail heavily rounded. It is, of course, magnetic. Some early 19th century coin patterns for die engraving transfer reduction were made of cast iron in England. Cast iron objects are usually foundry casts.