“Chalkopyrite crystals with indigo-blue covellite coatings together with transparent quartz crystals. The two little white aggregates on the chalcoyrite crystal in the upper part of the photo is the mineral preisingerite. There is a little single crystal of preisingerite on top of the group of quartz crystals to the right. Collection: Heinz Förch Photo: Michael Förch Analyzed by H. W. Graf, Jülich ”