I''m interested to see what other gemologist have to say about this. I don''t think I''d classify that cavity in your image as leaving a knife edge or making an otherwise normal girdle rate extremely thin however. I''d note it on the plot and in the notes and the girdle would rate as if that blemish/inclusion were not there. The ISG does not rate typical naturals,chips and cavities against girdle thickness. They are considered clarity characteristics and are noted thusDate: 11/23/2006 11:33:26 AM
thank you for your reply Belle.
C Smith I found this on the GIA edu site and it seems to say a cavity can affect girdle width
An extra facet, natural, chip, cavity or indented natural
located on the crown or pavilion at the girdle edge can
narrow the girdle at this location.In these cases,the remaining
area is considered in the thickness assessment even
when the feature is located at a “hill” position (see figures
10 and 11). If a “knife-edge” is created, the girdle thickness
is reported as extremely thin. If a chip, cavity or
indented natural breaks through the girdle onto the crown
and pavilion, the effect on girdle thickness is not considered
in the assessment (see figure 11).All of these characteristics
are accounted for in the diamond’s clarity grade.
Rockdoc how could a severely indented natural change the girdle measurement to ex thick? It would be indented.Date: 11/23/2006 1:13:28 PM
I think this is a stone by stone call that CANNOT be generalized.
I have seen examples both ways..... i.e. changing the girdle measurement from ex thin to ex thick due to naturals/extra facets which are extreme. I''ve also noticed this with severely indented naturals too.
An additional issue is how uniform and straight the girdle is. Most gem lab reports don''t graphically show a wavy girdle.