(IDEX Online) - High-value Type IIa diamonds have been found during explorations in Canada.Vancouver-based Arctic Star says analysis of a small sample - 12 stones over 0.3mm diameter - showed half were Type IIa.Only two per cent of diamonds globally are Type IIa - the most chemically pure, with no measurable nitrogen or boron impurities. Arctic Star drilled the Sequoia Kimberlite, on the Diagras diamond property, in Northwestern Territories, last year and has now released analysis of the stones it recovered. It says there are encouraging signs that they'll recover large diamonds, over 50 carats, from the kimberlite.A very small number of active diamond mines regularly produce Type IIa diamonds, notably Letseng, in Lesotho and Karowe in Botswana. Type IIa stones are frequently either top white colors (D, E, F, or G) or shades of brown.Many high-value, top color, large specials (+10.8 carats) are Type IIa diamonds, which include all 10 of the largest known rough diamonds recovered worldwide.Buddy Doyle, Arctic Star's vice president of exploration, said: "The presence of a significant proportion of Type IIa diamonds in the Sequoia kimberlite complex caustic fusion samples is another line of evidence of the potential to host plus 50ct, high value diamonds, backed up by the collaborative indicator chemistry and the relatively coarse, low gradient diamond size distribution."Further drilling is now taking place.Generic pic courtesy Arctic Star