I suspect there may be a slight overgrowth (or natural plating?) of silver in a couple areas-- in the some places the copper crystals have a distinctive silvery sheen, and I know that silver did occur in this area-- it's just that on most pieces they were tiny little dendrites, they weren't like this.  Again, just a suspicion but correct or not, it's still a very nice miniature example of this material, with a centrally positioned cuprite sitting on a cluster of well formed copper crystals!