The 40 pieces that comprise the gem-rich Ophir Collection, the property of an anonymous collector who amassed them over two decades of world travel, are now for sale. Among the notable items:1. The world’s largest sapphire (left) certified by Guinness World Records and weighing in at 31,308 cts., making it the size of a dinner plate.2. The world’s largest cut tanzanite, which weighs 508.06 cts., also certified by Guinness.3. Another Guinness record holder, the world’s largest cut brown sapphire at 5,905 cts.4. Two pieces of neptunite, a gem so rare that these two specimens are the only two the GIA has ever examined.5. A 15.43 ct. hibonite, also considered among the rarest gems on Earth.