Red diamonds are fancy-color diamonds that are so rare that only a handful are found each year and only in a few mines worldwide. They are the most expensive type of diamond, costing more than ...

The Oppenheimer Blue sold on Wednesday for more than $57.5 million including fees at a Christie's auction in Geneva, making it the most expensive diamond ever sold.

If the speculation is true, Zendaya's cushion-cut diamond would rank as one of the most expensive celebrity engagement ... minus the occasional "SNL" joke and red-carpet appearance.