What you see here is solid smithsonite (rare in any form from Arizona, in fact, but particularly as manifested here). In the center, you can see the super-sharp rhombs which were originally calcite, but were entirely replaced by smithsonite, molecule by molecule, retaining the original form of the calcites. The reddish surface color is from iron oxide. Ex. Dave Stoudt, William Hiss and the University of Arizona Mineralogical Museum Collections.