is an Hydrated Calcium Sulfate with formula CaSO4-2(H2O) and hardness of 2.
One of the most common mineral on earth,but is also one of the most difficult stone to cut. It's softness and the easy cleavage ( can be peeled off easily and scratched by finger nails),therefore is a big challenge by the cutter.Of course the polish result cannot be as perfect as in other stones,but still acceptable. Some minor inclusions visible at naked eye. It comes from Ribolla, near Grosseto,Italy.
This gem has been published on Rivista Gemmologica Italiana as one of the typical italian gems.
Weigth: 49.27 ct.