SASKATCHEWAN and NUNAVUT – Shore Gold of Saskatoon recently announced that 26% of all the diamonds exceeding 2.7 ct from the Star underground bulk sample are Type IIa diamonds.
Type IIa diamonds are rare, says the company, and account for probably less than 2% of all natural rough diamonds in the world. Only a small number of active mines regularly produce Type IIa diamonds, most notably the Letseng mine in Lesotho.
Type IIa diamonds contain no nitrogen or boron impurities and are frequently either top white colours (D, E, F or G) or any shade of brown. Many pink and brownish-pink diamonds are also Type IIa. Type IIa diamonds usually have anhedral crystal shape and exhibit a range of elongated, distorted or irregular morphologies. Most importantly, many high-value, top colour, large specials (greater than 10.8 carats) are Type IIa diamonds, including all of the 10 largest known rough diamonds recovered, from the 726 carat Jonker to the 3,106 carat Cullinan, according to information provided by Shore Gold (www.ShoreGold.com).
Meanwhile, Vancouver-based Peregrine Diamonds has discovered an additional kimberlite, CH-18, at the Chidliak project on Baffin Island. The discovery was made 16 km northwest of CH-13 and 15 km northeast of CH-12, the closest known kimberlites. Drill intersections at CH-18, which lies under a lake, were interpreted in the field as being both magmatic an pyroclastic in nature.
Peregrine is also taking a 12-t mini-bulk sample from its CH-6 kimberlite. The sample taken in 2009 yielded 4,737 diamonds larger than the 0.075-mm sieve size and included 109 commercial-size diamonds.
A map showing CH-18 and anomaly 291 and a map and diamond results from CH-6 are available at: http://www.PDiam.com/i/pdf/chidliak471.pdf.