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Diamond Cutter Question: Gia 4.79Ct H/vs2


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I recently was offered a 4.79CT H/VS2. The stone has a large table and small crown height. All else fine for the modern round brilliant cut.
Question; Can I re-cut this to GIA XXX without much weight loss? I would like to modify:
CH: 15%
TABLE: 60%
I presume this would have to be done by making the table smaller by 6% and increase the crown height by 3.5% hence having to lower the girdle location: leaving the TD where it is at 58.4%
How much loss do you expect I would incur, I’m sending the proportion graphic to my cutter but would like to hear your thoughts as well.
Regards R.K.



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How much weight loss are you willing to accept?  What is making the symmetry only "good".  My guess based on the information you have provided is that you should be able to maintain a 4ct stone but much of it depends on the symmetry and how much you will have to bring the girdle in to control that symmetry.  If it is the culet that is off, you may have to tilt the whole stone.  Maybe somebody with a Sarin can plug in the numbers and give yo a more accurate read, but I think you will only get an accurate estimate form somebody if they are able to see the actual stone.

Edited by GeorgeDI
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Quick, approximate calculations indicate that assuming a "trivial" symmetry issue (e.g. non-octagonal table, which is going to be recut), you could get away with a knife girdle and a (mostly) crown recut bringing weight down by ~45 points without shifting the (bottom of the) girdle, getting a 34.5/57 with the same depth , 40.8° PA and fixing the out-of-round at the same time.


Do I want to cut a 0.2% girdle on that stone? No way.


Apart from that, George makes very valid points. In my opinion, worth getting a cutter's opinion, but I'd be cautious. The milkiness I'm not so worried about - you can see that easily; SB is still going to make it difficult to sell, though.

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"non octagonal" is what GIA calls it... which is shorthand for "not a regular octagon", though of course it's still more likely to be an octagon than anything else (I suppose someone could cut a hexagonal table, and Solasferas have 10-sided symmetry... but the issue here is equal sides/equal angles rather than how many).


Yes, GIA stumped the myth in 1997, but the discount is still there.

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