BGO12 Bismuth Germanate Facet Rough pyro 1x 80 degree index gear

1x 80 degree index gear (ideal for cutting D20s)

This means that depending on the application you might see crystals that only have Nd or ones that are almost entirely Ce with just a pinch of Nd

showing a silky chatoyance caused by twinning

084 ie 2x diamond) and enchanting colors with a strong color change

Note that the camera exaggerates the red at the expense of the green--they do look better in person

BGO12 Bismuth Germanate Facet Rough pyro 1x 80 degree index gearThese 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