BGO12 Bismuth Germanate Facet Rough Marked Letter:1pc 6-7g This means that it shows

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

It weighs in at 82g and measures about 31x28x28mm

no durability issues and good optical properties which make it sparkle brilliantly

and on a black background it sometimes takes on a green cast

It likely didn't quite make it through QC before final shaping

BGO12 Bismuth Germanate Facet Rough Marked Letter:1pc 6-7g This means that it showsThese 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