The intergrown cluster of chalcopyrites on this bed of needle quartz are the most lustrous example of this mineral I have ever seen. The two largest crystals measure about 1 cm on an edge, and they are accompanied by a half dozen or so small crystals. The faces of the crystals are not completely flat and are crisscrossed with many minute striations, which help identify this as chalcopyrite rather than pyrite. This is an exciting piece from a mine further south in Mexico than I usually go. I hope more come out...and soon!