I purchased a neodymium-doped yttrium aluminum garnet from a surplus auction that included electro-optical equipment (big lasers and such.) The garnet is a nice pink color with a high refractive index. It's slightly bigger than 1 cubic centimeter and being lab grown it has zero defects other than the neodymium atoms which turn it pink.

I plan on having it cut and set into a ring. However one obstacle is that yttrium is considered toxic to humans as a dust. Proper safety, ventilation and cleanup must be observed which makes it difficult to find jewellers that are willing to accommodate this.