These are facet rough of an unusual experimental laser garnet from the Soviet union, codoped with Erbium and (likely) neodymium. The base color ranges from orange-pink to purple-pink, and they color change from more orange to more pink depending on the light source.
This is a new material for us from an old collection, a 40-year-old failed experimental laser garnet from the Soviet Union. It is clearly doped with Erbium, and like our modern pure Er:YAG it has a striking combination of orange and pink colors and a remarkable color change. Unlike pure Er:YAG it has a stronger pink component, suggesting the addition of another dopant like Nd, and the color is also somewhat lighter as well. Most of the material was grown via HDSM aka the 'boat method', though a few pieces were clearly czochralski pulled. From doing further reading we learned that the inventor of the HDSM method was a soviet scientist and was working on erbium yag laser material in the 80s, so it all seems to check out. Codoping Nd and Er can apparently produce a laser with a dual wavelength output which is incredibly useful so it all kind of checks out. We even have a good guess as to why this material didn't make the cut--aside from the variable base color some larger pieces show noticeable color zoning which means the codopants were not evenly mixed, which is not great if you want to make a laser.
Overall, it's a really cool material, and while I'm sure they were frustrated by the production problems their loss is our gain. This cuts amazing gems with a rich peachy-pink color-changing padparascha-like color. It also isn't one of those color changes that you might kind of see if you use a special flashlight or a lighter flame--the change is easily visible under real world lighting conditions and the stones look different throughout your daily routine.
YAG in general is an ideal material for faceting, which a high hardness of 8.5, no cleavage, no problems with polishing and excellent optical properties with an RI of 1.82. It is considered one of the easiest materials to facet.
