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Calling the pricescope experts RE: HCA, recutting.

@Rockdiamond - only playing devil's advocate here ;) lol, but there could be some irony read into the posts above, where on one hand you have said that using one's eyes is most important and that if you need tools to see differences, it probably doesn't make a difference, but the Octavia is lauded for its extreme cutting accuracy :P lol :D
 
Hi ooohshiny
For cutting the Octavia which is based on an extremely specific set of parameters, remarkable tools are required for cutting. Yoram actually invented one to use. But that's cutting.
For selecting one, I'd use the eyes as the final arbiter.
For selling them, the tools are very handy to prove the precision. But the eyes still gotta approve.
 
ccmans said:
Hello!

I was surprised when I recently saw that the GIA Ex stone I own is rated 5.5 on the HCA. When I bought it I had no idea about the HCA or any of this stuff, just that I should only buy GIA Ex or AGS0. I thought the stone looked nice (and still do!), but alas it is not for me, it's for her. My question is: if she doesn't find it brilliant enough, would it be possible to recut just the pavilion angle? Here are the specs.

1.2 ct
SI1
Table 60
Depth 61.3
Crown 33.5
Pavilion 41.6
Lower half 80%
Star 55%
4% girdle

I tried the HCA with 41 as the pavilion angle and it came up to a 1.9. I know there are risks to recutting a stone, but in your expert opinions is it worth looking into have the pavilion angle reduced? Or is there really no guarantee that a reduction like that would really help?

Thanks for your opinions! If she's happy with it I'm happy (haven't given it to her yet), but I'm just checking what my options are if she doesn't like it!

Unfortunately I dont think returning it is possible!
Click to expand...
I now have my dongle back at work. The pavilion only recut is the most effective because the weight loss is small. The rather thick girdle means Tolkowsky is possible with no diameter loss because the girdle can be reduced to thin and enable the crown recut to 34.5 and 57% - but the weight loss is at least 0.06ct
Capture2.png Capture1.png Capture3.png
 
Thanks a lot Gary. Seems like the pavilion only cut is the way to go. I compared the image you showed for my stones current dimensions to the ideal scope reference chart here:

https://ideal-scope.com/reference-chart-ideal-scope-images/

While it doesn't look excellent or very good, it doesn't seem as bad as the good image and below. Is this because this representation can't fully replicate an idealscope image?
 
It will be a very bright stone, brighter than a Tolkowsky, but slightly less fire.
But as GMK said - we are working from GIA rounded numbers and no idea of symmetry etc.
Talk with a good appraiser like Dave Atlas or Neil Beaty etc and ask them to supervise the process.
 
Grr.. I just double checked my GIA report and got some of the numbers slightly wrong in my OP.

1.18 ct (not 1.2)
depth: 61.4% (not 61.3)
star 50% (not 55)
Also, I'm not sure its a calculable attribute, but the report lists excellent symmetry.

Shouldn't change much in the renderings you posted above right?

I'll be talking to an appraiser for sure. I have sent out an email to Brian Gavin diamonds, and I'll look up those individuals as well. Thank you Gary, you've been a great help.
 
1.18 ct means that your diamond will likely lose less value if it drops to a 1.14 compared to than if it dropped from a 1.2 to a 1.16. Other than that I don't think it changes too much.
 
if we are going to help we need the entire cert, not bits and pieces
 
LightBright said:
Please share and explain what DiamCalc is to us novices...

Thanks to everyone for contributing to this very informative discussion.
Click to expand...

http://gmsoft.somee.com/psdiamcalc.xlsx

BTW this is nothing to do with the program, I think I saved it as that because it made sense at the time. This is just an excel sheet I put together as an amateur.
 
The main benefit will be the reduction in face up color. I would trim the pavilion only - the additional brightness will wash away more of the yellowish tint (I made the model spectra about J and turned off the fire / dispersion).
The stone is shallower than the GIA angle specs because of their dopey rounding.

Capture4.JPG

Capture5.JPG

Capture6.JPG
 
bmfang said:
gm89uk, tried looking at that xlsx file but I keep getting errors when trying to download it.
Click to expand...
Hi bmfang. Seems to be working now. Don't think I have much bandwidth allowance!
 
bmfang said:
gm89uk, tried looking at that xlsx file but I keep getting errors when trying to download it.
Click to expand...
Hi bmfang. Seems to be working now. Don't think I have much bandwidth allowance!
 
Thank you very much Gary. I now have a plan if it comes to this.

This forum has been very helpful.
 
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