Sotheby's has announced that the 555.55-carat black diamond is one of the largest to be auctioned. Aside from the stone’s caratage, it also has 55 facets and shaped like the Middle-Eastern palm symbol Khamsa which also means “five” in Arabic. Source: michael-bowles.com

Sophie Stevens, jewellery specialist, Sotheby’s Dubai

The Enigma diamond could sell for as much as US$6.8 million, with Sotheby's saying that they will also accept cryptocurrency payment. Source: michael-bowles.com

The Enigma's unique cut was inspired by the Khamsa, a Middle Eastern symbol of a hand meant to offer protection that is associated with the number five, which is reflected in both the diamond’s 555.55 carats and its 55-facet cut. Source: michael-bowles.com