A 16.08 carat rare pink diamond sold for more than $28.55 million (28.73 million Swiss francs) at Christie's Geneva Magnificent Jewel sale.

The largest cushion shaped vivid pink diamond in the auction was purchased by a Chinese client based in Hongkong. The private buyer dubbed the diamond as "The Sweet Josephine".

The gem is set in a platinum and gold ring surrounded by a double row of pave set white diamonds, and a third row of small pink diamonds underneath. The gem sold above its pre-sale estimate of $23 million to $28 million, according to Reuters.

The rare pink diamond shows no trace of secondary color, Christie's said, as reported on Forbes, while most pink diamonds exhibit a color modifier like purple, orange, brown or grey.  The gem is classified as a Type IIa diamond, which means it contains - if any - nitrogen for fewer than 2% of all diamonds.

The pink gem had earned  "Fancy Vivid" colour grading from the Gemological Institute of America (GIA). The gem has an absolute rarity as only one of 100,000 diamonds possesses a deep enough color to be qualified as "Fancy".

The gem is one of three pure vivid pink diamonds of over ten carats have appeared for sale in almost 250 years of Christie's auction history. The vivid pink diamond owned by an American family for the past 15 years. When it was purchased about 15 years ago, it was worth between $5 million and $8 million.

Christie's auction came as a part of a two-day blitz of high priced jewellery sales in Geneva. The rival Sotheby's offers the 12.03 carat Blue Moon Diamond with a pre-sale estimate of $35 to $55 million. Sotheby's sold a 59.6 carat pink diamond dubbed as "Pink Star" for $83 million in 2013, but it was bought back by the auction house after the buyer failed to pay.

Colored diamonds have become the center of attention in the jewel sales in Geneva, as they become increasingly attractive investments. The diamonds offer safer places for global rich to store their wealth. Colored diamonds prices are up 48% over the past five years and 149% over the past decade.

Head of Sotheby's international jewellery division David Bennett said, according to The Guardian, that the colored diamonds have seen sustained growth during the last few years. Partly because of their rarity, but equally because of their beauty.

Christie's also sold the second highest priced art in the auction, a Modigliani nude painting, to a private Chinese buyer for $170.4 million.