Chalcophyllite is a rare secondary copper arsenate mineral occurring in the oxidized zones of some arsenic-bearing copper deposits. It was first described from material collected in Germany. At one time chalcophyllite from Wheal Tamar in Cornwall, England, was called tamarite, but this name is now discredited (not to be confused with the amphibole mineral taramite, which is quite different). At Wheal Gorland a specimen exhibiting partial replacement of liriconite, Cu₂Al(AsO₄)(OH)₄·4(H₂O), by chalcophyllite has been found. The mineral is named from the Greek, chalco "copper" and fyllon, "leaf", in allusion to its composition and platy structure. It is a classic Cornish mineral that can be confused with tabular spangolite.