Graduate Gemologists on crack?

[kelpie]

Are there some days that GIA gemologists smoke crack before grading diamonds? I''m looking at this triple excellent one (4.3 HCA) and this "very good" ex, ex one (1 HCA but looks black) and thinking what system are they using that these are considered cream of the crop? Are they using their eyeballs or just numbers? JA also returned these in a search as "ideal cuts". They also have many beautiful stones of similar carat/color/clarity that are cheaper, am I missing something? Sorry if I offend anyone, I''m just a little shocked at the premiums these stones command when I really can''t look at them without getting the willies.

 

[Lynn B]

Hmmm, with all due respect, I''m not sure I understand why those stones gave you the "willies"? I looked at each diamond, and dragged the loupe over them both, too. I only looked quickly at the cert of #1, and I''m sure the HCA dinged it because of the deep pav angle... but with the shallow crown angle, it seems to work... I think the diamond looks fine.

The second stone''s being "black" is likely just the photography, again, I think the stone is probably lovely.

Just my humble 2 cents, and I am no expert. But believe me, I have seen plenty of stones that give me the "willies" (milky white, dull, flat, seriously [visibly] included, *dead*, etc.) but those two stones aren''t two of them!

 

[february2003bride]

Looking at ANY object that blown up and magnified isn''t attractive.

The black you are seeing on the diamonds are the arrows. When the camera obstructs the light return, the arrows pop up (and if that''s wrong, please correct me). Look at my avatar of my old diamond. The arrows are extremely clear and BLACK but in real life, they weren''t. They just gave off rainbow flashes.

Also, I don''t think you''ll get much help with the tone in which you posted.

 

[DiamondExpert]

To my knowledge, neither the GIA grading (system) nor the HCA were handed down on stone tablets...The man from OZ (the man behind the curtain) will correct me if I''m wrong

!

Consider both the strengths and weaknesses of the systems that you use, including your own biases - and we all do, and should, have them - to evaluate a diamond, especially from a distance.

 

[Lynn B]

Date: 2/9/2008 4:12:56 PM
Author: DiamondExpert
To my knowledge, neither the GIA grading (system) nor the HCA were handed down on stone tablets...

LOL!!!
Too, too funny!

 

[strmrdr]

1st one is a shallow steep with some leakage and so-so optical symmetry.
not excellent in any way.
I also suspect the gia rounding is making this stone look better than it is.
With better cutting a stone with such rounded numbers that fall in other zones of the rounding and better cut might be a nice stone but not top end.

The second is an extreme shallow/shallow
It is an excellent pendant stone.

The first would look pretty bad in any setting the second would rock in a pendant where it was viewed at a min of 2 feet.
http://diamonds.pricescope.com/ideal.asp
look where 33/40.4 falls on the chart, well into earring and pendant territory.

The use of any cut grading system for selection is not as easy as look at the numbers and decide!
That is why the HCA is a rejection tool.
It is saying reject the first one and further review the second one.
In this case it did exactly what its spose too do.

Now as far as the JA system again it uses a look up chart and should not be used as a selection tool and too be honest isn't a very good rejection tool either.
There are a lot of places that similar scales too rank stones and they don't work.

Now for the GIA system, GIA moved shallow/shallow combos down to VG because they are at best VG for a ring.
At the same time they allow some with steep pavilions into EX because the difference is hard too see by eye in some lighting. In this case they were wrong.
All systems are going to wrong a certain percentage of the time.
Look up charts more so than others.
The next step is ray-tracing a 3d scan which AGS does which falls into the trap of the selected parameters not fitting the real life stone.
Works well for rounds and OK for princess cuts but sucks for asschers.

The next step up and which the PS consumers use is too look at multiple data sets and tools and the opinion of a respected vendor who has the stone in front of them and then decide.
That is a formula that works.

 

[strmrdr]

Date: 2/9/2008 3:40:59 PM
Author: Lynn B

The second stone''s being ''black'' is likely just the photography, again, I think the stone is probably lovely.

close to the truth, the camera is too close to be optimal for that stone, it needs less head shadow and will work well in a pendant but is at best VG in a ring which the picture reflects
The JA camera system is set too show the amount of head-shadow needed to make mainstream super-ideals look good, I find it pretty useful for weeding out leakers and stones that are best in earrings and pendants.
It is very consistent in regard too head shadow which cant be said of many setups.

 

[Garry H (Cut Nut)]

Storm''s assesment is on the money. The shallow stone appears to have some pavilion painting too - but it is hard to tell from the photo.
GIA does use the numbers. They do not look at the diamond - it is entirely numbers based except for the polish, sym and girdle thickness.