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Cavity

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pyramid

Ideal_Rock
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Found this picture in the archives here, could an expert tell me would a cavity on a girdle like this affect the graded girdle width?

ags0004590101gs3@30xa.jpg
 

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pyramid

Ideal_Rock
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Sorry I attached the wrong photo.

It is this cavity I am wondering if a cavity of this nature affects the graded girdle width?

CGJSI2 cavity on girdle.jpg
 

belle

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obviously, not an expert here, but i''ll throw out my .02 and say that the particular inclusion wouldn''t effect the measured girdle width because there are obviously thicker (stage left) and thinner (stage right) portions of the girdle already.
since the thickest and thinnest portions are what are reported and this inclusion falls (by size) in between those extremes, it won''t effect the overall measurement.
 

C Smith

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A natural,nick or cavity would not affect the girdle width/thickness measurement. It would appear on the plot and/or in the notes on a grading report though.
 

pyramid

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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.
 

C Smith

Shiny_Rock
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Date: 11/23/2006 11:33:26 AM
Author: Pyramid
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.
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 thus
 

belle

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i got 'feather' in my head because of the first pic and didn't realize that the second pic was of a cavity. a cavity is a piece of the diamond that is 'missing'. obviously, if you have a piece of the girdle missing and the remaining portion (above or below) is thinner than normally acceptable, it will effect the width.
i think my (very lame) attempt at making the 'cavity' more pronounced and the area of the remaining girdle obviously thin, you can see how such an inclusion would effect the measurement.

cavitycausingknifeedge.jpg
 

RockDoc

Ideal_Rock
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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.

Rockdoc
 

pyramid

Ideal_Rock
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Thank you everyone for your replies.

C Smith the note and the photo were not shown together, ie. it was not a description for the photo saying about an extremely thin girdle. Don''t know if you thought I meant that or not from your reply.
 

pyramid

Ideal_Rock
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Yes Belle your photoshop version does look a lot like the one in the above link where the note came from.

That is a wonderful photo you did, so life like, I love the way you put the marks of other inclusions on the pavillion under the cavity too, or maybe that was the foot of the cavity.
 

pyramid

Ideal_Rock
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Date: 11/23/2006 1:13:28 PM
Author: RockDoc
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.

Rockdoc
Rockdoc how could a severely indented natural change the girdle measurement to ex thick? It would be indented.

How can you tell when a natural is on the edge of the girdle whether it is an inclined natural or an indented natural anyway? According to the site I mentioned about if it breaks onto the crown it is an indented natural, but Kenny''s stone (which experts think is not a natural) was deemed to maybe have a natural and it was on the edge of the girdle and onto the crown but looked in no way indented.
 

pyramid

Ideal_Rock
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Is the difference between a slope and whether it is digging into the stone?
 

pyramid

Ideal_Rock
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After reading some old posts in which pictures were posted of inclined natural and indented natural I now realise the difference is the digging into the stone part. I don't know why but a picture of an inclined one I had looked at previously where a part of girdle was straight above the incline seemed to look wrongly as though the inclined part was digging into the stone. I think this is the difference between seeing things like this on a computer screen as compared to seeing it in a three dimensional view with the eyes.
 
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