CHALCANTHITE IN FLOAT FROM A KYANITE MINE, CENTRAL VIRGINIA
SEM and EDS investigation indicates that the cations present are solely Cu and S, with O being the only anion observed. Crystals commonly occur as near-anhedral pinacoids commonly 5 to 15 micrometers in maximum dimension. Smaller euhedral crystals approximately 1 to 2 micrometers in length occur on the surfaces of larger crystals. Near-anhedral crystals commonly have fractures one micrometer wide and tens of micrometers in length. These fractures combined with the fine grain size enhance the dissolution of the mineral. Powder X-ray diffraction identifies the mineral as chalcanthite, (copper sulfate pentahydrate).
Under normal freshwater pH conditions the Cu2+ ion is stable and is toxic to bacteria and invertebrates. Although the quantities observed here likely pose no major environmental threat, if an ore body is encountered again with similar properties the material should be closely monitored.