These are faceted white GGG, Gadolinium Gallium Garnet. Each is labelled with its weight and letter in the photo and they can be purchased individually. A and B are a light golden color while the rest are colorless.
GGG is an exotic lab-created garnet and an old classic of industry and the gem world. It it was once grown for gem usage and because its dispersion closely matches diamond it has a very similar appearance, but once CZ hit the scene and got insanely cheap the demand for other gem crystals plummeted. Today it is just grown as an industrial crystal, primarily grown as a growth substrate, a material whose crystal lattice makes it useful for growing other, harder-to-grow crystals on top of it. It was also a vital component of bubble memory back in the day, which is a fascinating story of its own.
In the gem world it is prized for its optical properties, with a dispersion in particular that is very close to that of diamond. Faceted GGGs look very much like a diamond in terms of fire
GGG has a hardness just over 7, is easy to cut and good for use in jewelry though I wouldn't recommend it for a ring.
