A massive to crystalline sphalerite matrix hosts a striking blue, 3.4 cm scalenohedral crystal. This crystal began as calcite but was replaced (pseudomorphed) or at least coated a blue mineral, sometimes labeled as 'cuprian gypsum', 'cuprian melanterite' or ktenasite. Minor chalcopyrite scattered about on the matrix. Without chemical analysis its nature is uncertain. Regardless, the color combination gives visual appeal. Self standing and in superb condition. Previous dealer label gives a collection acquisition date of 1968.