Mosandrite
モサンドライト
6.06 ct
Octagon Cut
15.10 x 8.20 x 6.40 mm
Mt.St. Hilaire in Canada
max9423

Mosandrite is  a rare earth mineral : Sodium, Calcium, Titanium, Zirconium and Cerium silicate

with formul: Na(Na,Ca)2(Ca,Ce,Y)4(Ti,Nb,Zr)(Si2O7)2(O,F)2F3   and hardness of 4.
Extremely rare to be find as cut stone; it is found  in the Kola Peninsula and the

Mt.St. Hilaire in Canada like the gem you see here. Minor part of Eudyalite.