Tsodilo Resources Limited, the international diamond and metals exploration outfit has revealed that kimberlite BK16 contains rare and valuable Type IIa diamonds. The company has had possession of the diamonds that were previously recovered from BK16.
Left is the magnetic first vertical derivative ground magnetic data and the right is the Bouger gravity first vertical derivative data for the BK16 license area. (Pic By Tsodilo)
The stones have been stored with I. Hennig & Co. at the Diamond Technology Park (DTP) in Gaborone since Tsodilo took possession. They were recently cleaned by Lucara Diamond at its facilities at the DTP and then analysed by a Tsodilo technical staff member supervised by Hennig personnel using a Yehuda ZVI colorimeter, with one stone in Parcel 1 (25 stones total) and seven stones in Parcel 2 (83 stones total) being consistently identified as ‘Type IIa white,’ all grading as D color with no or only a faint level of fluorescence.
Tsodilo President and COO, Dr. Mike de Wit, said one cannot emphasize enough the importance of BK16 containing Type IIa diamonds.
“Recent and more well-known examples of Type IIa diamonds are the 1,111 carat, 813 carat and 374 carat diamonds all recovered in the later part of 2015 from the Karowe mine owned by Lucara and located 16 miles from BK16, with the 1,111 carat ‘Lesedi La Rona’ diamond being one of the largest gem quality diamonds ever recovered, second only to the famous Cullinan diamond, and the 813 carat stone, ‘The Constellation’, recently selling at auction for over US$63M,” de Wit said.
”It remains to be determined whether BK16 holds such historic diamonds as the Karowe mine, but it is encouraging to know that BK16 does contain Type IIa diamonds”.
Diamonds are classified as either Type I or Type II, with Type I diamonds containing nitrogen while Type II diamonds are nitrogen free. Type II diamonds (both Type IIa and Type IIb) are very rare and generally thought to comprise less than 2% of all diamonds.
Scientifically speaking, Type IIa diamonds are almost pure carbon diamonds, containing no significant amount of nitrogen in the crystal lattice. Since nitrogen is the impurity in diamond that imparts a yellowish hue, the lack of nitrogen results in a pure, very valuable colorless (D, E or F color) diamond.
While it is possible to obtain D Flawless diamonds from Type I diamonds, the most sought after diamonds are Type IIa flawless diamonds. Type IIb diamonds are similar to Type IIa diamonds in their lack of nitrogen, but they are also infused with boron, leading to a desirable blue tone within the stone.
Type II diamonds have superior optical properties and have a superior overall polish to Type I diamonds. Type IIa diamonds dominate the special stone size fraction, i.e., stones greater than 10.8 carats. Such famous diamonds as the Cullinan (the world’s largest cut diamond found in the South African Premier Mine in 1905) and the Koh-i-Noor (Urdu for “Mountain of Light”), which was found in India and now rests in the Tower of London, are Type IIa diamonds.
The Letšeng mine (Gem Diamond Limited) located in the Kingdom of Lesotho and the Karowe mine (Lucara Diamond Corporation “Lucara”) in Botswana are two mines currently producing some of the largest and most valuable Type IIa diamonds in the world.
