Since 1940, the Williamson Mine in Tanzania has been one of the world's few sources of gem-quality "bubblegum" pink diamonds. On Friday, the mine's owner, Petra Diamonds, announced that it recovered an extremely rare 23.16-carat pink diamond of exceptional color and clarity.
The mining company described the gem as its most significant recovery from the mine to date and will offer it for sale in Antwerp next month as part of Petra's December tender process. It is said to be of a much better quality than the 16.4-carat diamond recovered at the same mine in September 2014. That stone was sold for $2.2 million.
Vivid pink diamonds of exceptional size and quality are highly coveted in auction circles. Earlier this month, for example, a cushion-shaped 16.08-carat pink diamond was purchased by Hong Kong billionaire Joseph Lau for $28.5 million ($1.7 million per carat), setting an auction record for any vivid pink diamond. The gem’s selling price slightly exceeded Christie's pre-sale high estimate of $28 million.
“Pink diamonds are only found in a handful of mines throughout the world and their rarity ensures that they are one of the most highly coveted of all the fancy colors,” the company said in a statement.
The most famous pink gem originating at the Williamson Mine was unearthed back in 1947 and gifted that same year to Princess Elizabeth and Prince Philip upon their wedding. The generous gesture was made by Canadian geologist John Williamson, who was the original owner of the mine.
The 54.5-carat rough diamond was cut into a round brilliant that weighed 23.6 carats. It was named the Williamson Pink and set into a flower-motif brooch in 1952 by Cartier. Some people believe that the Williamson Pink was the inspiration for the Pink Panther diamond of movie fame.
Even though the Williamson Mine has been operational for 75 years, geologists believe the mine still has significant production ahead of it. The mine, which sits atop the Mwadui kimberlite pipe, has yielded about 20 million carats, so far, but should generate an additional 40 million carats. The mine's average depth is only 30 to 35 meters, and theoretically it could continue to yield diamonds as deep as 350 meters.
It is believed that pink diamonds owe their color to the effects of intense pressure and heat while they were still deep within the earth. These factors caused distortions in the diamond's crystal lattice that influence the way the diamond absorbs green light, thus reflecting a pink hue.
Colored diamonds are in the elite 1% of the world's diamond production, and pink diamonds make up 1% of the 1%, noted gem expert Richard Revez in a December 2014 interview with the BBC.
The Williamson Mine is currently co-owned by Petra Diamonds and the government of Tanzania, which holds a 25% stake.Credit: Petra Diamonds; Christie's; Google Maps.