These are fantasy cut GAGG lumogarnets with bubbles. Some are more included than others, and some have a decent afterglow. Each is pictured individually.
Cerium GAGG is a material which has recently risen to prominence in industry but never been used as a gem until now. It is what we call a 'lumogarnet' - a lab created garnet with incredible fluorescence. It glows a bright yellow, slightly greener and brighter than already-bright Ce:YAG. This material is like an upgraded version of the classic GGG crossed with an aluminum garnet (like YAG and LuAG) to give it excellent hardness (8) while maintaining a high RI (1.9) and generally excellent gem properties.
Some of these glow in the dark! Growers work very hard to make sure GAGG does not glow in the dark since it lowers the temporal resolution of the system (you want to know where an x-ray is now, not where it was an hour ago!) but sometimes they make mistakes, and a small subset have a stronger glow. In particular these bubbly stones have a higher rate since they're already messed up in another way.
