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Question regarding GIA cut and holloway

P: 4/25/2009 8:10:12 PM
kath1969 Rough Rock Total Posts: 8 Last Post: 4/26/2009 Member Since: 8/20/2008	I am looking at 3 GIA certified diamonds. Two are "excellent" cut and one is "very good" cut. Interestingly, I ran them through the holloway cut advisor. The two excellent cut diamonds scored a 4 while the very good cut diamond scored under 2. Is this possible?
Posted: 4/25/2009 8:10:12 PM

There are 7 replies to this message. There are 7 replies on this page.

P: 4/25/2009 8:26:31 PM
Stone-cold11 Ideal Rock Total Posts: 6,939 Last Post: 11/25/2009 Member Since: 9/9/2008	Yap, it is possible. Give us the numbers and we will explain to you why it is so for each case.
Posted: 4/25/2009 8:26:31 PM

P: 4/25/2009 10:21:41 PM
Garry H (Cut Nut) Ideal Rock Total Posts: 11,587 Last Post: 11/25/2009 Member Since: 8/16/2000	Date: 4/25/2009 8:26:31 PM Author: Stone-cold11 Yap, it is possible. Give us the numbers and we will explain to you why it is so for each case. Thanks StoneCold, also remeber the VG can be downgraded for other reasons like girdle sym and polish Garry Holloway FGAA DipDT HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au
Posted: 4/25/2009 10:21:41 PM

P: 4/25/2009 11:50:09 PM
kath1969 Rough Rock Total Posts: 8 Last Post: 4/26/2009 Member Since: 8/20/2008	The first two: 1.06 G SI1 6.46 6.49 4.03 Cut: Excellent Polish: Excellent Symmetry: Excellent Depth 62.2 Table 58 Crown 35.5 Pavilion 41 Girdle Med to Slightly Thick 1.09 G VS2 6.58 6.63 4.08 Cut: Excellent Polish: Very Good Symmetry: Very Good Depth 61.8 Table 58 Crown 35.5 Pavilion 41.2 Girdle thin to slightly thick The last one: 1.00 G SI1 6.33 6.44 3.95 Cut: Very Good Polish: Excellent Symmetry: Very Good Depth 61.9 Table 57 Crown 36.5 Pavilion 40.4 Girdle medium to slightly thick
Posted: 4/25/2009 11:50:09 PM

P: 4/26/2009 4:21:53 AM
Stone-cold11 Ideal Rock Total Posts: 6,939 Last Post: 11/25/2009 Member Since: 9/9/2008	The first two have a steeper pavilion angles for the respective crown angles, this will result in light leakage. If you look at the graph of the HCA for each table size, the green dot outline represents what GIA defines as it's Ex cut candidates. That also includes a large amount of green and blue, which are less than ideal in performance. For the third stone, it's angles are outside what GIA considered as Ex cut, but AGS will consider it Ideal cut, HCA also consider it a good candidate for further investigations. Just different range of angles that each lab consider as Ex/Ideal in this case. For us, I would consider #3 stone further, for example asking for an IS/ASET image to see if I like the light return and symm, checking if eye-clean, etc... Hope that answer your question.
Posted: 4/26/2009 4:21:53 AM

P: 4/26/2009 4:45:34 AM
Lorelei Ideal Rock Total Posts: 34,291 Last Post: 11/25/2009 Member Since: 4/30/2005	The first two diamonds are actually what we call steep deep, this means both crown and paviilion angles are not a good fit for each other. This can result in light leakage with these types of diamond. These angle combos can get the GIA Excellent cut grade unfortunately and can routinely score badly on the HCA. You can do better. The third looks the most promising so if you could get ASET or Idealscope that would be helpful then we can check it out for you. Can you get these images? The third diamond will probably got VG cut due to the pavilion angle. Nothing is more sacred as the bond between horse and rider...no other creature can ever become so emotionally close to a human as a horse. When a horse dies, the memory lives on because an enormous part of his owner's heart, soul, very existence dies also...but that can never be laid to rest, it is not meant to be... - Stephanie M Thorn
Posted: 4/26/2009 4:45:34 AM

P: 4/26/2009 10:02:11 AM
kath1969 Rough Rock Total Posts: 8 Last Post: 4/26/2009 Member Since: 8/20/2008	Thank you so much for the replies. The third diamond is the least $'s because it is slightly smaller and rated a very good cut. I haven't viewed the diamonds yet, but it will be interesting to see them side by side and see if I can pick up on the difference.
Posted: 4/26/2009 10:02:11 AM

P: 4/26/2009 10:04:40 AM
Lorelei Ideal Rock Total Posts: 34,291 Last Post: 11/25/2009 Member Since: 4/30/2005	Let us know how you get on. Nothing is more sacred as the bond between horse and rider...no other creature can ever become so emotionally close to a human as a horse. When a horse dies, the memory lives on because an enormous part of his owner's heart, soul, very existence dies also...but that can never be laid to rest, it is not meant to be... - Stephanie M Thorn
Posted: 4/26/2009 10:04:40 AM

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