These are Yttrium Orthovanadate, aka lab-grown wakefieldite. This is an unusual crystal grown for use in lasers, and it comes in a range of colors depending on the level of neodymium added in. WE have it in pink, blue to blue-green, yellow, orange and some bicolors. Note that the purples show a dramatic color change to green under fluorescent lighting!
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.
