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

In sunlight it has a strong golden hue while some indoor lights will make it more pure yellow or more orangeish

Fortunately for us these uses require very exacting standards and sometimes crystals are rejected

but these glass laser rods are an exception

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