Ken was an expert on fine Chinese minerals and when these came out about 4 years ago they were very quickly absorbed into the collector market. They are comprised of chalcocite which were then coated with iridescent chalcopyrite due to the addition of iron in the solution. Ken held two back, which, according to him, had the largest crystals of all he had seen. These were never inexpensive, but I priced these relative to the lower market, so they are an excellent value. Ex Ken Roberts collection. Locality: Tongshan Copper Mine, Daye, Hubei Province China Composition: copper iron sulfide and copper sulfide
