In alchemy, chalcanthum, also called chalcanth or calcanthum, was a term used for the compound blue vitriol (CuSO4), and the ink made from it.
ɪn ˈælkəmi, tʃˈælkænθəm, ˈɔːlsoʊ kˈɔːld tʃˈælkænθ ɔːɹ kˈælkænθəm, wʌzɐ tˈɜːm jˈuːzd fɚðə kˈɑːmpaʊnd blˈuː vˈɪtɹiːəl kˈuː sˌoʊ fˈoːɹ, ænd ðɪ ˈɪŋk mˈeɪd fɹʌm ɪt.