Clarity Grading Question

[Moh 10]

Is grading done only looking into the crown of the diamond?

And is it even physically possible (because of the way light reflects in diamond material) for a flaw to exist that is not visible looking into the crown?

IOW, could a stone with a high clarity like VVS or IF have inclusions which are visible only when looking into the pavilion, which would not affect the grade?

 

[John P]

Date: 12/4/2008 10:11:15 PM
Author:Moh 10
Is grading done only looking into the crown of the diamond?

The grade is based on the face-up view. However all inclusions seen at 10X are plotted (face-up and down) so it is possible to have a VVS1 stone (example) where minute inclusions may be visible only through the pavilion.

And is it even physically possible (because of the way light reflects in diamond material) for a flaw to exist that is not visible looking into the crown?

Sure. Pinpoints are a good example. There may be much more in fact, since the grade is set at 10X. Start zooming in to 20, 30, 40, 100X and you're going to see all kinds of things that were invisible at 10X.

IOW, could a stone with a high clarity like VVS or IF have inclusions which are visible only when looking into the pavilion, which would not affect the grade?

The only characteristics plotted are those that help set the clarity grade, establish the stone's present condition or identify it.

Do remember that plotting is done separately from grade-setting. The clarity grade is set first, based on examination at 10X. Then the characteristics, per above, are plotted. The majority will be plotted in the crown diagram, with the exception of characteristics that reach the pavilion surface and those that can only be seen face down. The latter are plotted on the pavilion diagram.