The 303-carat pear-shaped Golden Canary diamond is a fancy colour brown-yellow stone that is the largest diamond to have been graded as internally flawless by the Gemological Institute of America. It fetched $US12.4 million ($AU18.35 million) at Sotheby’s. Image: Cedric Ribeiro

Originally known as the Incomparable Diamond and discovered in the Democratic Republic of Congo in the 1980s, the diamond was recut from its previous 407-carat shield shape to deepen the colour. The diamond was discovered as an 890-carat rough. Image: Cedric Ribeiro

The emerald ring was discovered on the Atocha, a Spanish vessel that sunk in 1622. Image: Sotheby's