The D–Z scale in practice
A D–F stone appears colourless to most viewers in most settings. G–J stones are near-colourless and represent excellent value. K–M begin to show warmth visible face-up. Below N, colour is clearly apparent.
The grade gap between adjacent letters is consistent in the laboratory but variable to the eye, depending on cut, shape and mounting. A round brilliant in a platinum solitaire shows colour more readily than the same stone in a yellow-gold halo.
Fancy colours
Fancy intense and vivid yellow, pink, blue and green diamonds operate under entirely separate grading logic. Colour saturation and distribution become the primary value drivers — the D–Z scale does not apply.
Investment-grade fancy colours are among the rarest physical assets in the world. Provenance and laboratory origin reports are essential for this category.
