Smithsonite after Calcite - San Giovanni Mine, Sardinia, Italy
 
Yellowish smithsonite as an encasing pseudomorph after calcite. The calcite crystals are completely dissolved, but can still be seen clearly in the shape of the smithsonite. 
Pieces of such a quality with such a good luster and intense color are extremely rare to find on the market. 
Rarely aesthetic collectible of unique quality from this find in Sardinia.