Biggest Colorless Diamond Could Fetch $20 Million

London (Bloomberg News) -

A pear-shaped colorless diamond is estimated to sell for $20 million at an auction in Switzerland.

The D-color flawless stone, weighing 101.73 carats, will feature in a jewelry auction by Christie’s International at the Four Seasons Hotel des Bergues Geneva on Friday. It is the largest colorless diamond of this optimum grade to appear at auction, and 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 in an e-mail. The stone was recently cut from a rough diamond, weighing 236 carats, that had been 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 (meaning “place of small stones”) open pit diamond mine, the world’s richest by value, 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 as their even rarer colored equivalents. The record price for any gem at auction is the 45.4 million francs ($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 colorless stone is the 20.4 million Swiss francs ($21.5 million at the time) with fees paid for the 76.02-carat Archduke Joseph Diamond at Christie’s, Geneva, in November 2012.

From this week, more buyers will be charged top-rate 25 percent fees at auctions held by Christie’s International and Sotheby’s.

Bidders at Christie’s New York will be charged the maximum premium on items with hammer prices of as much as $75,000. The upper threshold had previously been $50,000. The ceiling at which buyers are charged 20 percent increases to $1.5 million from $1 million.

Sotheby’s introduces similar changes on March 15. The band of lots incurring a 25 percent premium increases to $100,000 from $50,000. The 20 percent threshold rises to $2 million from $1 million. Both companies continue to charge 12 percent fees for the most expensive items.

“It’s part of the relentless drive to optimize auction- house profits,” Patrick Jefferson, the London-based antique furniture dealer, said. “This kind of tinkering with thresholds will soon be forgotten. People won’t stop wanting to buy wonderful things.”

Lots priced at less than $50,000 have been the least profitable for the world’s biggest auction houses. Up until this month, lower-value items represented one percent of their sales, according to data provided by the Cayman Islands-registered art fund, Artemundi Global.

The new thresholds will increase the share to two percent at Christie’s and three percent at Sotheby’s, the fund said in an e- mail.

Traditional auction houses are facing increasing competition from low-cost online companies. Sotheby’s and Christie’s are reluctant to accept lots below certain undisclosed minimum values unless they are part of a larger consignment, dealers said.

“These changes will be a disincentive to sell at the lower end,” Jefferson said. “The big auction houses are only interested in selling cheaper things if they cross-pollinate with more expensive areas of the market.”

In London, the new 25 percent top premium has been set at 50,000 pounds at Sotheby’s and 37,500 pounds at Christie’s, rising from 25,000 pounds at both houses.

Christie’s has also increased the percentage of premium charged at wine sales. Buyers will now pay 22 percent on top of hammer prices in New York and Hong Kong, and 17 percent in London, Paris and Geneva, increases of one and two percent respectively.

Sotheby’s structure of 22.5 percent at New York and Hong Kong wine sales and 17.5 percent in London is unchanged.

This is the first adjustment to Sotheby’s and Christie’s auction premiums for more than four years. Buyer’s fees were introduced in 1975. Dealers were enraged at the time and continue to resent being charged for purchases.

Phillips declined to comment when asked if it was adjusting its premium structure. Bonhams’s fees remain unchanged.