These are orange glowing samarium YAG (Yttrium Aluminum Garnet) with an orange-yellow base color and strong orange fluoresence. Each individual stone is labelled with its carat weight and letter in the photo and they can be purchased individually.
This is an unusual lab garnet, samarium-doped YAG. This material is mostly used for measuring pressure in high-pressure diamond anvil experiments--the color of its fluorescence actually changes depending on how much pressure it is feeling. It is an uncommon material so we actually convinced one of our suppliers to grow a crystal of it for us--they had never grown Sm:YAG before so it is an experimental boule.
With a hardness of 8.5 it is ideal for use in all kinds of jewelry.
