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: cut stone> 6.5x6.7x3.6 mm.
Weight: 0.84 ct.
size of crystal: 7x9.5 mm
weight of crystal : 2.40 ct.