The Collaborative International Dictionary
crocus Martis
Colcothar \Col"co*thar\ (k[o^]l"k[-o]*th[~e]r), n. [NL. colcothar vitrioli, fr. Ar. qolqo[.t]ar.] (Chem.) Polishing rouge; a reddish brown oxide of iron, used in polishing glass, and also as a pigment; -- called also crocus Martis.