These are faceted labmade LuAG (Lutetium Aluminum Garnet). We have calibrated rounds, squares and trillions, as well as individual fancy cut stones. Each fancy cut stone is labelled with its letter in the photo and they can be purchased individually. The variation dropdown shows the carat weight and measurements of each stone.
LuAG is an exotic lab-created crystal with the same structure as natural garnets, but a composition and properties which are impossible in nature, particularly its outrageously strong green fluorescence which makes it glow when exposed to sunlight and even some indoor light. This is what we call a 'lumogarnet' - a lab created garnet with incredible fluorescence, designed to help detect invisible radiation. This is one of my favorite synthetic materials--brilliant and hard enough for use in all jewelry (mohs 8.5!).
The fluorescence really is crazy--even normal room lights will make a LuAG gem fluoresce, and outdoors with indirect sunlight can make it look like it is photoshopped into real life. A blacklight aimed directly at it makes it insanely bright. It is just a great material overall, perfect for the collector and jeweler alike.