Diamond cut (GIA)
Excellent to Poor — and issued ONLY for standard round brilliants. Fancy shapes have no cut grade, because only the round brilliant has standardised facets.
| Property | Value | Authority |
|---|---|---|
| Scale range | Excellent to Poor [1] | — |
| What it measures | How the diamond interacts with light, plus design and craftsmanship. Face-up appearance is assessed on brightness (total internal and external reflection of white light), fire and scintillation. [1] | — |
| Applies to | STANDARD ROUND BRILLIANTS ONLY. Cut grades are given only to round brilliants because they are the only cut with standardised facets; all other shapes are called fancy shapes and receive no cut grade. [1] The most commonly misunderstood limit in diamond grading. Looking for an "Excellent cut" oval is looking for something that does not exist. | — |
| Viewing condition | Face-up appearance, plus design and craftsmanship. [1] | — |
| Grades in full | Excellent, Very Good, Good, Fair, Poor. The major components of a standard round brilliant are the crown, girdle and pavilion; the large flat top facet is the table. Every round brilliant has 57 or 58 facets, the 58th being the culet, a tiny flat facet at the base of the pavilion. [1] | — |
Sources
- GIA — Diamond Cut — Gemological Institute of America (GIA 4Cs, Diamond Cut)