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
Size: 25.7x13.1x4.8 mm.
Weight: 16.73 ct.