This mine now owned by Petra Diamonds still remains the most regular purveyor of type IIb color diamonds, 10 to 20 times rarer than the IIa.
An extraordinary fancy intense blue gem weighing 122.52 carats was discovered at Cullinan in June 2014. The jewelers mapped with accuracy its internal crystalline regularity by using the semiconductor characteristics that are specific to the type IIb diamonds.
This non-destructive analysis enabled to optimize the cut. Four diamonds were produced. The Cullinan Dream is the biggest of the four. It is rectangular with cut corners and weighs 24.18 carats. Its clarity is VS2. It is estimated $ 23M for sale by Christie's in New York on June 9, lot 261.
This diamond is exceptional. Its fancy intense hue is much rarer than the fancy vivid blue. The Oppenheimer Blue, identified as the largest fancy vivid blue ever offered at auction, only weighed 14.62 carats. It was sold for CHF 57M including premium by Christie's on May 18, 2016.
An estimate around $ 1M per carat looks consistent with results obtained on other blue diamonds. A fancy intense blue with an excellent VVS2 clarity weighing 7.64 carats was sold for CHF 9M including premium by Sotheby's on 11 May 2010.
The other highly rare variety of blue, the fancy deep blue, can reach a price per carat of the same level or even higher. The estimate by Sotheby's in April 2016 at $ 2.6 million per carat for the diamond of Shirley Temple was nevertheless much exaggerated.
SOLD for $ 25.4M including premium
Please watch the video shared by Christie's to announce the Cullinan Dream: