is a Sodium Iron Silicate with formula NaFeSi2O6 and hardness of 6-6.5.
Is an opaque mineral,often with small pits or fibrous structure. Most famous are the crystals from Malawi like this stone here,but it is found also in other locations in the world .
Size: 15.5x7x5.5 mm.
Weight: 5.45 ct.