These are faceted, lab-created day-glow GAGG (Gadolinium Aluminum Gallium Garnet).
Cerium GAGG is a material which has recently risen to prominence in industry but never been used as a gem until now. 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. It is what we call a 'lumogarnet' - a synthetic garnet with incredible fluorescence. It glows a bright green-yellow, brighter than the already-ridiculously-bright Ce:YAG. Like Ce:YAG and LuAG it is used as a scintillator to help detect invisible radiation.
These stones have a very bright green-yellow fluorescence which gives them a super bright and almost uncanny glow in some lighting. These stones also glow in the dark to some extent, though not as much as our high glow GAGG does. Still, it is a neat feature!
