copperas : Idioms & Phrases
blue copperas
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noun hydrated blue crystalline form of copper sulfate
blue stone; chalcanthite; blue vitriol.
WordNet
White copperas
(Min.) , a native hydrous sulphate of iron; coquimbite.
Webster 1913
Yellow copperas
(Min.) , a hydrous sulphate of iron; called alsocopiapite .