Lab green sapphire is one of the trickier colors to grow. We belive most materials have eithet cobalt and or nickle which can take on different valence charges effecting the color. Atmosphere, temperature, and additives are used to control the saturation and color of the final crystal. Crystals are often patchy in color and have low color saturation. We have some exceptional examples of very high quality materials that are rarely produced compared to some other colors of sapphire.