is a recently discovered beryl containing Cesium as impurity with formula Be3Al2(Si6O18) .
There is debate regarding Pezzottaite vs Vorobyevite and choromophores , Cesium cannot be responsible for any colors, instead the bluish color of Vorobyevite is due to iron traces,as far as I know.This question remain open and more studies need to be done in order to find out the true. Nevertheless is a quite rare and interesting gem material; only small stones can be cut and often cloudy or included with parallel tubes-like with sometimes cat's eye effect.
It comes from Badakshan Province,Afghanistan and here is offered together with a natural crystal.
Size of gem: 5x5x2.7 mm.
Weight of gem: 0.34 ct.
size of crystal 7x9 mm.
weight of crystal: 2.28 ct.