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.