Blue Argyle Diamonds are considered to be one of the world's most rare and valuable gemstones. Graded by Argyle as Blue-violet or Blue-Grey, these stones are unique to the Argyle mine, as they receive their colour from traces of hydrogen, as opposed to other Blue Diamonds which get their colour from Boron. The combination of Argyle blue and pink diamonds in a select amount of Pink Kimberley Jewellery make for some of the rarest and most unique pieces on the planet.