a variety of Diopside with composition of Calcium Magnesium Manganese Silicate and formula CaMgSi2O6 ; hardness around 6.
Uncommon material,often mixed with other minerals,opaque to translucent.
It is found in few location in the world.This stone here comes from the classic type locality:
Praborna Mine,Saint Marcel,Aosta Valley,Italy.Unusual pattern!
Size: 18.5x18x3.6 mm.
Weight: 15.44 ct.