Aga Khan emerald, world's most expensive green stone, fetches record $9 million at auction

A rare square 37-carat emerald owned by the Aga Khan fetched nearly $9 million at auction in Geneva on Tuesday, making it the world's most expensive green stone.

Sold by Christie's, the Cartier diamond and emerald brooch, which can also be worn as a pendant, dethrones a piece of jewelry made by the fashion house Bulgari, which Richard Burton gave as a wedding gift to fellow actor Elizabeth Taylor, as the most precious emerald.

In 1960, Prince Sadruddin Aga Khan commissioned Cartier to set the emerald in a brooch with 20 marquise-cut diamonds for British socialite Nina Dyer, to whom he was briefly married.