The Oppenheimer Blue Diamond — $57.5 million (2016)

The Oppenheimer Blue Diamond sold for $57.5 million in 2016 at Christie's Geneva, achieving a record $3.93 million per carat for a gemstone at auction. This vividly blue 14.62-carat stone, named after former owner Sir Philip Oppenheimer, outperforms #9 The Scream's per-unit valuation, as its per-carat price dwarfs the $119.9 million artwork's per-carat equivalent of roughly $800. Blue diamonds of this intensity are rarer than any other material on Earth, with only a handful ever discovered.