Elena, I have never cut the Chatam material, but I have cut many of
the Russian and other synthetic chrysoberyl that I think was
hydrothermal. Both have excellent color change when the stone is
orientated correctly. The Russian material seems to be a little blue
green to red purple. The best red to green I have seen is the
hydrothermal. I have cut 20+ carat Russian synthetics that have
spectacular color change, but the smaller hydrothermal stones, in the
2-3 carat range, have been more dramatic red to green color change.