Geneva, Switzerland — 15 March 2013 – A pear-shaped colourless diamond weighing 101.73 carats is expected to sell for US$20 million at a Christie’s International auction in Switzerland on May 15.

Bloomberg News reports that the D-colour flawless stone “’ the largest colourless diamond of this optimum grade to appear at auction “’ will feature in the Christie’s International jewellery auction at the Four Seasons Hotel des Bergues here. It is being sold by a client who wishes to remain anonymous.

This is the first time the gem has appeared for sale and the buyer will be able to name it, the London-based company said today in an e-mail. The stone was recently cut from a rough diamond, weighing 236 carats found at the Jwaneng mine in Botswana. It took 21 months to polish, said Christie’s.

Demand for the rarest diamonds as an alternative asset and portable store of value has pushed up prices in recent years.

The Jwaneng open pit diamond mine “’ the world’s richest by value “’ means “place of small stones”  and is jointly owned by De Beers and the government of Botswana.

At the top end of the market, “white” stones are regarded as less desirable than their even more rare coloured equivalents. The record price for any gem at auction is the US$45.6 million paid by the London dealer Laurence Graff for a 24.78-carat emerald-cut “Fancy Intense Pink” at Sotheby’s, Geneva, in November 2010.

The record auction price for a colourless stone is the US$21.5 million with fees paid for the 76.02-carat Archduke Joseph diamond at Christie’s, Geneva, in November 2012.

Source: Bloomberg News. For more information, click here.