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| Girdle heights calculation method |
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GIA method | Octonus method |
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Notes - extra facet adjacent to the girdle (from any side) with height more than 10° from Total Height is not a girdle facet and never affects girdle height calculation
- steep girdle extra facet has less than 15° deviation from the girdle plane
- shallow girdle extra facet - more than 15°
- a virtual model is built by removing the extra facets and the neighboring facets are continued until they intersect
- and meeting at least one of the conditions:
- with height > 10% from Total Height
- from pavilion side, with facet area > 1/580 from the total cut area
- from crows side, with facet area > 1/900 from the total cut area
...is not a girdle extra facet (it is a crown or pavilion extra facet)
- steep girdle extra facet has less than 15° deviation from the girdle plane
- shallow girdle extra facet - more than 15°
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- Uses real model:
- steep girdle extra facets are calculated as a part of a girdle
- shallow girdle extra facets are not calculated as a part of a girdle
| - Uses virtual model built on the real brilliant model by:
- leaving steep girdle extra facets in their places and calculating them as a part of a girdle
- excluding shallow girdle extra facets
- excluding caverns
- for RBC, in all HPO versions except 5.2.10 - excluding crown and pavilion extra facets adjacent to the girdle
- when excluding a facet, the neighboring facets are continued until they intersect
See examples and further explanations on the Building Virtual Model page | - Steep extra girdle facets are calculated as a part of a girdle.
- Uses real model and excludes Shallow extra girdle facets
during girdle heights calculation.
| Steep extra girdle facets are calculated as a part of a girdle.Uses virtual model built on the real brilliant model
but without Shallow extra girdle facets. |
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The following parameters are calculated differently:
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