Fine large Chalcopyrite crystals are surprisingly rare worldwide. This is a superb piece and outstanding from this old Mexican locality. Zacatecas is a classic locale and it has been noted for some fine Chalcopyrites, probably the best ever found in Mexico and among the best from all of North America. These are superb crystals, sharp, sizable and with a great patina. Overall the esthetics and arrangement are superb on this piece. Ex John Marshall collection, this has small Quartz and some minor Galena as well. The largest twin is almost 4 CM across but 2 CM is more typical. This is certainly an important Mexican specimen, the crystals are equal to the very best we have seen in any museum. It dates back to the 1970 era.