BGO12 Bismuth Germanate Facet Rough Marked Letter:1pc 6-7g specifically Bi3Ge4O12 aka evlitine) is

specifically Bi3Ge4O12 aka evlitine) is valued as an optical substrate because of its highly unusual electrooptical properties

Laser Alexandrite: An amazing material grown mostly for medical lasers

This means that it shows a mixture of red and green flashes

They are tan out of the ground and have to be treated to get a darker background

but these glass laser rods are an exception

BGO12 Bismuth Germanate Facet Rough Marked Letter:1pc 6-7g specifically Bi3Ge4O12 aka evlitine) isThese are BGO 12 aka Bismuth Germanate facet rough. This is a real cool rarity in the gem world. Bismuth Germanate (in this case, specifically Bi3Ge4O12 aka evlitine) is valued as an optical substrate because of its highly unusual electrooptical properties. It has exceptionally good optical properties too, with (as far as we can tell the literature is weak) an RI of 2. 15 and dispersion of 0. 1. Cut stones are incredibly beautiful with high brilliance