NEW YORK (Reuters) - A purplish-pink diamond in excess of 10 carats could fetch as much as $15 million when it is sold at a Magnificent Jewels auction next month, Christie's said on Wednesday.
The 10.09 carat Fancy Vivid cushion-cut is expected to be the highlight of the sale on April 12 in New York.
Prices for large pink diamonds have skyrocketed at auctions in recent years, with four pink diamonds going for more than $1 million per carat since late 2009, Christie's said.
Demand and increasing rarity have drive up prices, making them the most expensive coloured diamonds on the market.
"Collector demand for large coloured diamonds has never been stronger, especially where pink diamonds of this size and quality are concerned," said Rahul Kadakia, head of jewellery at Christie's in New York.
The auction house set a per-carat record for any diamond at auction in December 2009 when the Vivid Pink 5-carat cushion cut diamond sold for more than $2.1 million per carat in Hong Kong.
Fewer than 10 percent of all pink diamonds mined weigh more than .20 carats, Christie's said, and even fewer bear such deep colour saturation and brilliance as the gem that will be auctioned.
"I have never seen such vivid colour in a stone of this size," Kadakia said, adding that the gem had an even richer, deeper hue than a 6.89 carat Fancy Vivid purplish-pink diamond that fetched $6.9 million in December.
Pink diamonds get their colour through a rare, naturally occurring slippage of the crystallographic lattice in the stone while it is forming deep within the Earth's crust.
Only a few mines in the world produce pink diamond rough, and of the stones that are cut and polished, only one in about 10 million diamonds possess colour pure enough to be graded as Fancy Vivid, according to Christie's.
In December a 14.23 carat Fancy Intense pink rectangular-cut diamond sold for $23,165,968 at Christie's Hong Kong, setting an auction record for jewellery sold in Asia.