is a Calcium Boron Silicate with formula Ca(B2Si2)O8 and hardness of 7.5.
it a beautiful stone,not very common and can be easily set in a jewel withou any problem.
This piece here comes from Dalnegorsk,Primorskij Kraj,Russia.It is irradiated,but the color is stable. Custom cut by Luigi Mariani.
Weight: 6.44 ct.