Hydrozincite is an alteration product of smithsonite, sphalerite or hemimorphite. This fine specimen from the Tsumeb Mine features an aesthetic cluster of sharp, brown smithsonite crystals with a powdery dusting of gray hydozincite microcrystals on a nicely contrasting crust of calcite. The largest smithsonite rhomb, 1.8 cm, is perched at the top of the specimen. Ex. Rob Smith Collection.