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Information Needed for Opinions on A Round Diamond

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MissAva

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Often new posters to Pricescope will ask what information they need to post in order to judge a round. This is what I look for before I comment, thought this might be helpful.
The following are needed
Color
Clarity
Depth:
Table
Crown Angle and %
Pavilion Angle and %
Girdle
Culet
Polish
Symmetry
Fluorescence
Measurements
What Laboratory issued the grading report.
Idealscopes, and Magnified images would be nice as well. Price is needed if you want people to comment on whether or not it is a reasonable price.
If anyone else can think of information that would helpful please post it as well!
 

strmrdr

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Nov 1, 2003
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23,295
If asking for pricing info specify if the diamond is internet or b&m

If you have seen the diamond say so.
 

TheGreenZone12

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I can find most of that but for instance with the crown and pavillion numbers where would you get that? Here
is the page of the diamond that I am looking at and on both reports it provides I do not see any information concerning that?

http://www.bluenile.com/diamonds_details.asp?pid=LD00982048&filter_id=1

33.gif
 

Dancing Fire

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Regular Guy

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Subtle, but I think really helpful post, Matatora. This last question....



Date: 12/2/2005 11:51:54 PM
Author: TheGreenZone12
I can find most of that but for instance with the crown and pavillion numbers where would you get that? Here
is the page of the diamond that I am looking at and on both reports it provides I do not see any information concerning that?

http://www.bluenile.com/diamonds_details.asp?pid=LD00982048&filter_id=1

33.gif
TheGreenZone demonstrates the value, and the implications to what you say, as far as info you should have.

I agree, you should have this info to go forward, generally. And if you don't, maybe you shouldn't.

To have the info, you get the info, you should do one of two things:

a) go to a vendor that has the wherewith all to supply the info to you. This is typical of the on-line vendors, but not always, it would be for them only reliably for in-house diamonds if they have the measuring equipment (helim, sarin and ogi, more or less in that order of preference for quality of data), or could be applied to diamonds brought in. And so, in the case of an expected answer to theGreenZone, though you'd have to check their policy to be sure, I don't know that they particularly warrant that for the diamonds they sell, a majority of which are virtual, and not in-house, that they will get that data for you.

Or

b) buy a diamond with a document that does contain that data. AGS does this best. And, as it happens, TheGreenZone has a cherry pick. The presentation of the AGS certificate is tiny, so you have to use their magnifying glass to see it. In fact their more modern certs, of which this is one, when it shows the triple 0, including light performance, will tend to allow you to even forget all the rest. However, the rest is there, with crown at 35, pavilion at 40.8, table 56.3, depth 61.4, small culet, falling as expected right in the middle of the new AGS0 as might be expected from the triple 0, and when also applied to the HCA discussed here, yields a 1.5 xxxvg TIC...all really good news.
 

ademello

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Many Certificates Issued by labs as well as Independent appraisers may not list Crown Angle, Crown Height %, Crown Height in Millimeters as well as Pavillion Angle and Pavillion Depth %. A Good Gemologist in your area should easily establish these figures either through direct measurement, a Proportioscope or by proper GIA Accepted Estimation Techniques. Once These Figures are established You should have a good Idea of where this diamond falls in relationship to an Ideal Cut Diamond. Arthur DeMello GG. (GIA) Boston, Mass.
Date: 12/2/2005 11:51:54 PM
Author: TheGreenZone12
I can find most of that but for instance with the crown and pavillion numbers where would you get that? Here
is the page of the diamond that I am looking at and on both reports it provides I do not see any information concerning that?

http://www.bluenile.com/diamonds_details.asp?pid=LD00982048&filter_id=1

33.gif
 

Regular Guy

Ideal_Rock
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5,959
Nothing too personal, but, regarding accepted GIA practice....


Date: 12/3/2005 1:28:29 AM
Author: ademello
Many Certificates Issued by labs as well as Independent appraisers may not list Crown Angle, Crown Height %, Crown Height in Millimeters as well as Pavillion Angle and Pavillion Depth %. A Good Gemologist in your area should easily establish these figures either through direct measurement, a Proportioscope or by proper GIA Accepted Estimation Techniques. Once These Figures are established You should have a good Idea of where this diamond falls in relationship to an Ideal Cut Diamond. Arthur DeMello GG. (GIA) Boston, Mass.

perhaps it''s out of this we''re anticipating that with the new presentation of crown & pavilion data from GIA, it will be rounded data for table, crown and especially pavilion data, thereby increasing the boundaries of measurement error that would have been the case otherwise.

Specifically, regarding the use of the Proportionscope, I did inquire about this on this board some time ago, and find the answer consistent with my naive prejudices, inasmuch as, by the logic of what we read here as the basis of discerning the best from the good, tenths of a percent in measurement can make a significant difference, and without equipment sensitive enough to capture that difference, the effort might as well not be met.

For this reason as well, and despite Window shoppers validation elsewhere of more than one vendor as a safe refuge, were I to seek out an independent appraiser again (and I probably would), I think I''d want them to have sarin or better to evaluate the measurements of a round diamond.

I could be convinced otherwise on this, but this is the prejudice I''ve garnered here. Frankly, sadly, the better vendors here are most likely to have the most accurate measuring devices, and generally, they don''t also do appraisals.
 

JohnQuixote

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Great idea Matatora!
36.gif


To newcomers this can seem like a lot of data. It might help to list parameters as they commonly appear together.




Practically every grading reports provides:

LAB - Note origin, particularly if it's an EGL document

Measurements
Carat Wt

Depth %
Table %
Girdle
Culet

Polish
Symmetry

Clarity
Color
Fluorescence

* If this is all the report provides you will need to request a SARIN, OGI or HELIUM scan to get measurements listed below. Considering that most diamonds are a multi-thousand dollar purchase it is reasonable to insist on the additional data.


EGL and some others provide all the above, plus the following:

Crown Height % (crown %)
Pavilion Depth % (pavilion %)

* While somewhat useful, crown and pavilion % are not nearly as telling as crown and pavilion ANGLES. Angles should be acquired in every possible circumstance.


AGA, AGS, GIA 2006** and some others provide all the above, plus the following:

Crown Angle
Pavilion Angle
Star Length % *
Lower Half % *

* Star and Lower Half information will appear on GIA 2006 documents. It may be appearing with AGS (not sure about AGA... David?)

** On GIA reports these measurements are rounded to nearest .5 of a degree in CA, .2 in PA and 5% in SL and LH.





At the minimum, in order to use the CUT ADVISER, you will need depth %, table% crown angle, pavilion angle and culet description... And of COURSE the angles are only found in the last category
1.gif
.

A SARIN, OGI or HELIUM report will provide the necessary measurement information, and if the jeweler is having one run for you, you may as well acquire all of the other details.

1. Note that Sarin/Ogi/Helium reports for a diamond may have very slight differences from an accompanying grading document due to machine scan variance. Of the three Helium is most accurate but not widely available. Slight differences (+/- .2 of a degree for instance) are perfectly normal. In these instances the grading document is usually viewed as the authority.

2. GIA reports may differ more from Sarin/Ogi/Helium scans in CA PA SL and LH because of their policy to round those numbers.




As mentioned, it's helpful to tell us whether this is an online consideration, or you are actually able to see the diamond being described.




If the report has a proportions diagram on it (similar to the one below) you may find much of the information above on that diagram.



MatatorasThread.jpg
 
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