As the world’s only reliable source of natural pink diamonds and origin of more than 90% of all pinks, the Argyle diamond mine felt the need to develop a grading system which would be helpful in categorising the various colours and relative rarity of their diamonds.
The existing internationally recognised grading system for pinks and other coloured diamonds, established by the G.I.A. (gemological institute of America), while useful, was somewhat limited in differentiating between the pinks coming from Argyle. Argyle divided the pink production into 4 separate categories, in order of rarity – PP (purple pink), P (pink), PR (pink rose’) and PC (pink champagne). Within each category, the diamonds are further rated according to the STRENGTH of the colour, from the deepest colour (1) to the lightest (9), with the exception being the PC category which has only 3 strength ratings, 1 (the lightest) to 3 (the deepest). Thus, a grading of 1PP, represents the strongest colour (1) of the rarest category (purple pink) and would therefore – all other things being equal – be a much rarer and more valuable diamond than a 4PR for example.