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A brownish-red ferric oxide obtained as a residue after heating ferrous sulfate, used in glass polishing and as a pigment.
[Medieval Latin, from Spanish colcótar, from Arabic qulquṭār, possibly from Greek khalkanthos, copper sulfate : khalkos, copper + anthos, flower.]
(Elements & Compounds) a finely powdered form of ferric oxide produced by heating ferric sulphate and used as a pigment and as jewellers' rouge. Also called: crocus
[C17: from French colcotar, from Spanish colcótar, from Arabic dialect qulqutār]