pricescope
Ideal_Rock
- Joined
- Dec 31, 1999
- Messages
- 8,266
New article by David Atlas: Making the case for Imagem diamond grading.
There can be problems with simplification if the problem is not one to be simplfied. This problem is complex and because we have labs with complexity constraints we end up with a market that is 2/3rds round and princess cuts - that is bad for consumer choice and business creativity and excitement. The biggest issue I have with direct assessment is they can not be used to develop new cuts.
David,
Is Imagem now selling equipment to labs or is this service strictly available to US clients from you? Is Philly the only location where this can be done?
David,
Best of luck with your sales efforts! I know that you and Dr. Agarwal have been working on this for years and it sounds like it’s coming together. I certainly understand that the identity of potential clients is a sensitive piece of information. Keep us posted as it develops.
Gemprint as it has existed for the last decade or so has shut down operations and this may leave you an opening in the market for the Verigem service. Is that service currently available from anyone other than your labs?
GCAL purchased Gemprint Corp. and is using some of the technology as part of some of their services but clients who don’t live in NYC, or who don’t want to ship their valuable property to NYC, have no way of either getting a stone scanned or of matching a stone to a previous scanning to see if it’s the same. The service that was offered by Gemprint Corp. is no longer available to 99% of the customers who might otherwise be interested in it. GCAL may put together some sort of program in the future to make an identification and matching service available but, so far, I’ve seen no indication that this is in the works. In the meantime, there is no service available and the value of the Gemprint brand for this sort of thing is evaporating through disuse. Their plans seem to be other services entirely. We’ll see what evolves with them. Their loss may be your gain. If yours has additional functionality, that’s even better. I can’t say I want to prepay for $19k but when you get the pricing structure worked out, give me a call. I may be interested.
Dave the attached Gem Adviser File has a thick GIA girdle and 28 crown. This would be a highly desirable stone if shown to anyone who did not know its proportions. It has a 28 degree crown angle, 55% table and 60.3% total depth (pavilion angle is 41.55). It would be very difficult to chip this girdle as I am sure you would agree. (If you dug the upper girdle facets a little you could even improve this stone further).Date: 7/7/2006 8:48:27 AM
Author: oldminer
http://www.gemappraisers.com/lbidfs.htm This is an OPEN matter and has been on my website for several months. There has never been any secrecy involved. We always look for meaningful input and fair criticism. Your example of a 28 degree crown angle on a thick girdle makes good sense. We might downgrade the diamond for the thick girdle and/or the shallow crown angle. You can''t defend such a diamond as a finely crafted stone. It may be a great looking diamond, but not among the best cut ones. We lower the grade on DFS for faults of durability, finish and size (spread).
We''ll have some fun in San Diego!!!!!!!!!!!!! We will
thanks for reading Daveit is worth thinking about Dave - extra work - but it is how i would do it. Date: 7/8/2006 7:36:30 AM
Author: oldminer
It would be easy enough to alter the way DFS grades diamonds. it is worth thinking about Dave - extra work - but it is how i would do it. If the market agrees that these presently strange diamonds are desirable, then I have no personal problem with making changes toward that direction. We are fixated on Tolkowsky being the center of our present universe. You and a few others are the exceptions and you may find market acceptance at some point. I''m flexible as I see many diamonds that look excellent that are not exactly traditional ideal cuts.
Standards are tools we use to structure or expalin the market. If the market changes, the standards may need to be adjusted. As always, I look to learn about these things. Knowing more is far superior to being in the dark. THANKS
Date: 7/7/2006 9:27:15 PM
Author: Garry H (Cut Nut)
Thanks for your responses above Dave.
Only one remaining issue:
Dave the attached Gem Adviser File has a thick GIA girdle and 28 crown. This would be a highly desirable stone if shown to anyone who did not know its proportions. It has a 28 degree crown angle, 55% table and 60.3% total depth (pavilion angle is 41.55). It would be very difficult to chip this girdle as I am sure you would agree. (If you dug the upper girdle facets a little you could even improve this stone further).Date: 7/7/2006 8:48:27 AM
Author: oldminer
http://www.gemappraisers.com/lbidfs.htm This is an OPEN matter and has been on my website for several months. There has never been any secrecy involved. We always look for meaningful input and fair criticism. Your example of a 28 degree crown angle on a thick girdle makes good sense. We might downgrade the diamond for the thick girdle and/or the shallow crown angle. You can''t defend such a diamond as a finely crafted stone. It may be a great looking diamond, but not among the best cut ones. We lower the grade on DFS for faults of durability, finish and size (spread).
We''ll have some fun in San Diego!!!!!!!!!!!!! We will
This stone has a spread that is 2.5% better than Tolkowsky.
Thanks for pointing me to your standards.
I would be happier to see you using the approach we developed for DiamCalc that AGS subsequently used - one that relates spread to Tolkowsky or some such standard.
For example it is possible to make a diamond that has 63% depth and at 6.48mm (a nice 1ct size) the stone would weigh in at 1.17ct.
Firstly Bill, look at the black line in the chart above - Tolkowsky would have approved of all those proportion combinations. He used his formulas based on one starting point - one mid way thru the range.Date: 7/8/2006 9:06:53 AM
Author: He Scores
You gentlemen will pardon this Tolkowsky lover here for a moment won''t you?
Once again, I would like to say that diamonds are pieces of sculpture and not to be viewed ONLY in one position. Any system relying on this one particular view IMHO is weaker than Tolkowsky''s math or thin girdle on his model. You must remember that when Tolkowsky wrote about his model, the trade corroborated his findings by offering up their version of what they accepted to be high standards.
You don''t find this consensus today among the trade when it comes to these performing stones. Why? In short, because static face up view is not a worthwhile platform. Take the above stone for an example. First off, let''s just ASSUME that all the angles are 28 degrees. Which anyone knows they aren''t, won''t be, etc. but let''s say they are. This may or may not look good in the face up, but it would have such a lack of definition between all the facets on the crown that the stone would just ''lay'' there when looked at it from other angles.
To say that it would be a highly desirebable stone ''if someone didn''t know the proportions'' doesn''t seem applicable except to say that a lay person would say that stone is nice. That should not be the basis for any sort of standard, which by the way is what we should be striving for in the trade.
My reading of the pulse of the industry is that the trade does not want ''broader'' ranges for what is an excellent stone. This is tantamount to giving ''softer'' grades on color and clarity. You may think one would benefit by getting a better color (or read cut or clarity) on a report than the stone actually is, but that''s not the case. It leads to non-sales, returns of memo etc. Why? Because eventually someone who knows stones won''t accept it.
The trade wants, and is demanding, and eventually will get strict standards. You may poo poo Tolkowsky and his angles (which basically is all he gave us....the rest is simple basic math), but what he gave us is not sloppy. The Tolkowsky model is a model that is virtually unattainable to the the poor cutter at the wheel. The Tolkowsky model looks good from all viewing positions.
The face up look with the neked eye is not how this trade judges cut. I''ve done my own research on it. The face up look is just that. A face up look. Far too broad to ever be accepted as a standard for look, let alone cut.
Bill Bray
Diamond Cutter
The exceptions will never be common because of the choice that tolkowsky made.Date: 7/8/2006 12:23:50 PM
Author: oldminer
If the exceptions are truly common and valid then there is a problem, but if the exceptions are quite rare, unusual, worst case scenarios, or pipe dreams, then we can just say that we have solved the problem to a useful extent and we will address the strange exceptions when and if they become more common, problematic or solvable.
Have only this: http://www.diamondtalk.com/forums/showthread.php?t=54913Date: 7/8/2006 9:44:28 AM
Author: Garry H (Cut Nut)
Re the 28 crown stone - it is near or maybe over the limits, but I ran tests on that stone thru 30 degrees of tilt with DiamCalc for contrast and light return. It scores Vg and Excellent compared to Tolkowsky. It is rare to see such stones because they often are poorly finished - but that IS my point.
Some years back some detractors to HCA published info on a stone that they said proved numbers do not work. The stone had about a 25 degree crown angle and an accompanying deeper pavilion angle. They were blown away with it. It just happened to fit in a straight line with HCA had I extended past 28 degrees. (if anyone has a link to that thread i would love to find it again).
Thank you thank you, for finding this gem for me JulieNDate: 7/9/2006 7:04:57 AM
Author: JulieN
Have only this: http://www.diamondtalk.com/forums/showthread.php?t=54913
Cutting these stones is not on the small Master stone Study for the stones we have currently begun to cut Dave - but why dont you ask some of your participating manufacturers in India to do a few?Date: 7/9/2006 6:46:56 PM
Author: oldminer
I see a diamond with a 25 or 28 degree crown angle as not having such good light performance off the face-up view as a more accepted cut diamond. I could be totally wrong here, but shallow crown diamonds tend to look good face-up and lose more of their good looks within a narrow tilt versus a more standard crown height diamond.
Across 30 degrees of rotation / tilting this stone has 15% less contrast than Tolkowsky, but 21% better light return face up and 6% better thru rotation.
this is anything but an ugly stone Dave
The DFS hits thin and thick girdles with deductions. If a diamond has a ''Durability'' issue then it takes a discount in DFS. It might be a superb looking stone with a cutting fault. If it has a very thick girdle, then it becomes an issue of girdle thickness, versus better spread. It takes a ''Size'' deduction. as is this stone has too thin a girdle - but if it were polished with 4.5% at the mains (Thick) then its 0% better than Tolkowsky spread would have dropped to 4% better than Tokowsky - so spread is not going to Ding it Dave, and it would be hard to break at 4.5% I am sure you would agree? None of this means the diamond might not make a pretty stone worthy of consideration at a ''price'' that was suitable, but it will take years to convince this traditional trade that such a stone is a premium cut worth the same as the already current large crop of super cut types. Not if they were buying and selling with Imagem optical results? Cutters may learn to cut prettier, less costly diamonds and make better use of their precious rough material. This would be of benefit to the trade and the consumer. I believe the ImaGem grader will show these fine performing diamonds do exist if anyone gives us a physical example. I don''t doubt the predictive accuracy of Sergey and Jasper''s work. Maybe you have a few of these in your store since you seek out those diamonds which work with the Ideal-Scope regardless of how they are cut. I''d love to own a few of these examples for future R&D and for the simple knowledge itself.