BGO12 Bismuth Germanate Facet Rough pyro larger than a hen's egg

larger than a hen's egg and about the size of a duck egg

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

showing a silky chatoyance caused by twinning

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

BGO12 Bismuth Germanate Facet Rough pyro larger than a hen's eggThese 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