These are faceted lab-grown wakefieldite in calibrated, also known as yttrium orthovanadate. This material is very rare as a gem!
For larger individual fancy cut gems see https://store.turtleshoard.com/products/lab-wakefieldite-loose-gems-aka-yttrium-orthovanadate-nd-yvo4
YVO4 is best known for its role in some very specialized lasers. Like the more usual Nd:YAG it is a powerful lasing medium, but it has puts off a different wavelength and has other properties that make it preferable in some contexts. Nanoparticles of medical-grade YVO4 have also shown promise as a treatment for wounds, promoting healing and reducing scar formation, and potentially even for general longevity, though the research is still in very early stages.
As a gem it is a challenging cut, difficult to polish with a relatively low hardness of 5 (same as apatite and some glasses) and two directions of perfect cleavage. However the reward for cutting it are exceptional optical properties (refractive index 2.1, dispersion of 0.084 ie 2x diamond) and enchanting colors with a strong color change.
