Chalcanthum
In alchemy, chalcanthum, also called chalcanth or calcanthum, was a term used for the compound blue vitriol, and the ink made from it. The term was also applied to green vitriol.
Some maintained calcanthum to be the same thing as colcothar, while others believed it was simply vitriol.
The term "vitriol rubified" refers to the reddish iron oxide residue left after heating green vitriol, and should not be confused with "red vitriol," a distinct mineral.