I recently did a couple of postings about diamond cut and posted a diamond recut chart that can be used to give an estimate of how much weight would be lost to improve diamond cut.
Lets take a look at a real example on a stone. When purchased the stone was nice, but a little deep.
Prior to being recut it was 1.15ct so there was room to improve it without going below 1.00ct, which wold be a bad financial move.
Specs Before Recut
Carat: 1.15ct
Measurements: 6.59 – 6.65 x 4.26
Pavilon Depth: 64.4%
Table: 57%
Girdle: Medium – Slightly Thick, polished
Culet: None
Polish: Very Good
Symmetry: Very Good
Cut Grade: Very Good
The cut grade on the above stone would have very good, excellent would not be possible because of the depth being 64.4%.
Off to the cutter it went for a little tune-up.
Specs After Recut
Carat: 1.10ct
Measurements: 6.59 – 6.64 x 4.12
Pavilion Depth: 62.2%
Table: 55%
Girdle: Thin to Medium, Faceted
Culet: Very Small
Polish: Excellent
Symmetry: Very Good
Cut Grade: Excellent
The angle of the pavilion would need to be increased in order to give the stone less depth, resulting in a more impressive stone. When reducing depth you do not change the diameter of the diamond much. On this diamond there was no change in the face up size.
The final weight loss was about 4.34%, according to the diamond recut chart we should have lost about 4% going from a depth of 64.4% down to 62.2% so the chart was right on.