To my knowledge this gem is THE WORLD'S LARGEST CONCAVE FACETED NATURAL BLUE SAPPHIRE!!!!!!!! It takes weeks to accomplish this cut requiring the custom manufacture of many cutting and polishing spindles! Sapphire is the hardest gem on the planet next to Diamond and, so, is extremely difficult to cut and polish while dealing with all the grain relationships and the wearing out of even the slightest of concentricity forces one to retool and begin a facet again. A mind boggling gem in many many ways!!