GIA FacetScan question for peers

[Garry H (Cut Nut)]

Rhino I would be happy to recieve your plans for any future "research videos" so that there is a clear goal and we are sure the stones and techniques you use will be well thought out and carried thru with rigor.

The two stones are the ideal H&A''s and the shallow stone from my Journal article using Diamond Dock (I did not buy the steep deep).
I have attached the shallow stones Gem Adviser here. It has 59.3% table and 33 degree crown and 40.5 pavilion. This places the stone right on a Very Good / Good boundary - so with its actually only just got its GIA grade of Very Good.

If they could account better for painting then they should have bumped it down as it has a moderately painted crown (3.3 degrees or 0.9 notches). What this means is that about 13rd by surface area of the crown facets are 2.4 degrees shallower than they would be without painting. Effectively the stone has close to a 32 degree average crown angle.

Amazingly the 2 very senior GIA instructors (one is a course development manager) picked it over the ideal for brightness when they viewed it in Diamond Dock.

 

[Rhino]

Hey Garry,

Date: 9/1/2006 11:30:57 PM
Author: Garry H (Cut Nut)
Rhino I would be happy to recieve your plans for any future ''research videos'' so that there is a clear goal and we are sure the stones and techniques you use will be well thought out and carried thru with rigor.

I am certainly open to your suggestions. You can expect full cooperation from me and if there are lighting environments in which you think certain comparisons should be drawn I''ll carry it out and do them to the best of my ability according to your suggestions/instructions.

The two stones are the ideal H&A''s and the shallow stone from my Journal article using Diamond Dock (I did not buy the steep deep).
I have attached the shallow stones Gem Adviser here. It has 59.3% table and 33 degree crown and 40.5 pavilion. This places the stone right on a Very Good / Good boundary - so with its actually only just got its GIA grade of Very Good.

Excellent and thank you kindly for the GA file on the shallow combo. When Leo took us into the spot lighting that stone really jumped! What I found most interesting regarding that observation Garry was there were 2 stones which in my personal opinion, were great examples of stones that exceled in one lighting environment over another. For example the shallower stone I had preferred way more in direct lighting while not in diffuse lighting and the other stone (I''m guessing a slightly steep/deep) appeared brighter to me in diffuse daylight yet didn''t quite have the kick of the shallower stone in direct light. In diffuse light I was not able to determine a "ring of death". That is why I had made that comment to you afterwards "excellent example stones!" Watching John P. examine the stones I was noting that our focal lengths and body sizes over the diamonds were pretty much the same too. Perhaps that is a reason why we both arrived at the same conclusions. I''d be curious to see the the file on the other for reference if you have it available. If not basic Sarin proportion data would do.

If they could account better for painting then they should have bumped it down as it has a moderately painted crown (3.3 degrees or 0.9 notches). What this means is that about 13rd by surface area of the crown facets are 2.4 degrees shallower than they would be without painting. Effectively the stone has close to a 32 degree average crown angle.

Amazingly the 2 very senior GIA instructors (one is a course development manager) picked it over the ideal for brightness when they viewed it in Diamond Dock.

LOL. I know I had mentioned somewhere in the past threads over the months that observing diamonds in the DD has given me a greater appreciation for shallow angled combos and your personal bias towards them as reflected in the HCA. I totally relate. In fact in the current video I''m working on, after showing the varying appearances that qualify/disqualify GIA Ex vs GIA VG I make a very strong case for shallow angled combos should a person decide to go outside the GIA Ex/AGS Id zone. Of all people I think you will appreciate it most Garry. While I was talking with Al Gilbertson about the observation testing done he expressed to me how certain staff members REALLY liked some of the shallow angled combos too. RD16 & RD22 might be examples. The link you posted to above showing the graphic I had taken of the shallow stone alongside the steep/deep IMO really demonstrates it best, or the best I know how to via photography.

If you have any ideas for a survey I''m open to listening. My store is IMO a great enviroment because its always busy and I always have access to consumer input, many of whom will allow me to videotape too since I am friendly with most of the families who shop here. Also the front of our store is nothing but large windows with easy access to natural daylight as well as many other environments in various parts of the store (direct/diffuse/reflected ambient). An experiment I personally thought would be fun, educational and entertaining not only for us but also for the people of this forum would be to conduct/videotape an in-store survey, then video tape the same comparison and post a poll here on the forum to see if the results of what people are seeing live corellate to the poll here. Then after the poll is finished post up all the specs/data on each stone in the survey. If it works it will help people to correlate what appearances they prefer most in one diamond over another. It may or may not corellate but we''ll never know if we don''t try. I''ve been doing this privately with very good success. Let me know your thoughts on a comparison we should test it out with. If you''d rather pick up this conversation in email that''s ok too.

With kind regards,

 

[Garry H (Cut Nut)]

Rhino I told you which stone the other one is.

You are being bad again - reading what you might want to read.
So just go read my post again.
From reading it you can also find the proportions and indeal-scope / ASET and gIA''s data on it.
It might help understand why the other stone (that you think is steep deep) works best in what you call diffused light.

Think also about what "direct light" means.
Direct light must have come from a D.......n (please fill in the blanks)

 

[Rhino]

Sorry if I misread or overlooked anything. I''ll reread it again.