These are calibrated fantasy cut laser garnets (Nd+Ce:YAG) with concave facets. They come in violet and gold (depending on the ratio of Ce to Nd) and have variable fluorescence including yellow, pink, red and violet.
The laser garnets were grown varying chemistries, creating different colors ranging from pink to orange to gold to green, And the fluorescence has multiple colors too, with some stones showing both pink AND yellow at the same time. Some of these have bubbles, a natural consequence of the growth method that produces them and one of the reasons they didn't make it into lasers.
With a hardness 8.5, YAG laser garnets are ideal for use in all kinds of jewelry.
