The photo speaks for itself — this is a gorgeous, textbook-formed crystal of sapphire (corundum) showing both blue and yellow zones. 11.65 carats. Notably the yellow tip helps to prove it is not heated in treatment to enhance the blue color from a gray stone. Such sharp, colorful crystals are rare, as they are usually water worn and damaged. The lemon yellow tip makes this stand out from so many others! That is why Rock kept it since 1980, of course. Rock Currier Collection #4131.