Killer Tanzanite thumbnail that's also a great association piece too.  Fine, gemmy blue Tanzanite crystal with excellent luster and great transparency with attached large, single Prehnite crystals (analyzed) on the backside. Prehnite from Merelani is usually seen as rounded aggregates, yet on this specimen they occur as individual crystals to 7mm wide. In addition to the Prehnite, there are white crystals of an unidentified mineral also attached to the backside. A very nice Tanzanite, undamaged with TOP luster, good color and highly gemmy.