Diamond colour (GIA D-to-Z)
Runs from D for colourless to Z for light. It starts at D on purpose — GIA deliberately avoided A, B and C so the scale could not be confused with the inconsistent systems that preceded it.
| Property | Value | Authority |
|---|---|---|
| Scale range | D (colourless) to Z (light) [1] | — |
| What it measures | Absence of colour. Stones are compared against masterstones of established grade under controlled lighting. [1] | — |
| Applies to | Diamonds in the normal colour range. Diamonds occur from colourless through yellow, grey and brown to nearly every hue. [1] | — |
| Viewing condition | Controlled lighting, compared side by side against masterstones. [1] Colour is relative, which is why the comparison method rather than the eye alone defines the grade. | — |
| Grades in full | A continuous letter scale from D to Z. GIA begins at D as the top colourless grade specifically to avoid confusion, comparison or association with earlier systems that had used letters, numbers, Roman numerals and terms such as "blue white" — usages that caused misunderstanding and, in some cases, misrepresentation. [1] | — |
Sources
- GIA — Diamond Color — Gemological Institute of America (GIA 4Cs, Diamond Color)