Chalcophyllite is an uncommon, hydrated copper, aluminum, sulfate arsenate. In this case a vuggy matrix is studded with highly lustrous, emerald green crystals of chalcophyllite, to 5 mm across. This is from a single pocket find in a VERY rural, remote, old area of China. We found a few of them for sale at two China shows in the past, and then no more. AMAZING locality material for this species! So far as I know, this is one of the two best larger specimens. A shocking and unexpected find!