Until recently, the most expensive diamond in the world was the Oppenheimer Blue, a vivid blue diamond that sold for $50m last May. This has now been surpassed by the Pink Star diamond, a rare oval-shaped diamond that sold for $71m at auction earlier this month. The stunning 59.6 carat diamond is the world’s largest internally flawless, fancy vivid pink diamond ever graded by the GIA.

The diamond was discovered in 1999 by De Beers miners in Africa. The Pink Star was cut from a 132.5 carat diamond and it took two years of shaping, cutting and polishing to achieve the oval shape. It was valued at $60m at Sotheby’s Hong Kong but surpassed this estimate during a five-minute bidding war between three buyers. The winning bidder was Chinese jewellery retailer Chow Tai Fook, who later renamed the diamond CTF Pink.

In November 2013, the diamond was offered for sale and achieved a record $83m, but the buyer defaulted on the payment leaving the diamond in the Sotheby’s inventory. Before the sale of the Pink Star, the world’s most expensive pink diamond was the Graff Pink, an emerald cut diamond once owned by celebrity jeweller, Harry Winston. The Graff Pink was set in a ring and sold for $46m in November 2010 to diamond dealer Laurence Graff, who renamed it it Graff Pink.

Pink diamonds are a lighter form of red diamonds, which is the rarest diamond colour in the world. It is thought that the red colour is created by changes in the electron structure during the diamond’s movement to the surface. With the majority of diamonds, the colour is determined by other elements such as nitrogen (yellow diamonds) or nickel (green diamonds). Pink diamonds are highly sought-after for engagement rings due to the romantic connotations.

The sale of this incredible diamond could mark an increase in demand for fancy coloured diamonds. While the diamond solitaire engagement ring will always be a classic, more and more people are looking for unique and rare diamonds. As with all diamond grading factors, rarity equals value. As pink is a rare colour in diamond classification, this makes them very valuable.