The Collaborative International Dictionary
Crocus \Cro"cus\ (kr[=o]"k[u^]s), n. [L., saffron, fr. Gr. kro`kos; cf. Heb. kark[=o]m, Ar. kurkum, Skr. ku[.n]kuma.]
(Bot.) A genus of iridaceous plants, with pretty blossoms rising separately from the bulb or corm. Crocus vernus is one of the earliest of spring-blooming flowers; Crocus sativus produces the saffron, and blossoms in the autumn.
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(Chem.) A deep yellow powder; the oxide of some metal calcined to a red or deep yellow color; esp., the oxide of iron ( Crocus of Mars or colcothar) thus produced from salts of iron, and used as a polishing powder.
Crocus of Venus (Old Chem.), oxide of copper.
Wiktionary
n. (context organic compound obsolete English) polish rouge; a reddish-brown oxide of iron, used in polishing glass, and also as a pigment; crocus Martis.
Usage examples of "colcothar".
Her tawny mane, which fell long and unruly down her back, was somewhat darker than her colcothar pubic hair, which matched that which sprinkled down her legs to her dainty cloven hooves.
There are two mortars with their pestles just below the colcothar of vitriol.