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GIA / IGI grading comparison for 6 stones

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diamondnovice

Shiny_Rock
Joined
Sep 29, 2002
Messages
123
Hmmmm. Based on the information you have given.

Color grading:

50% of the stones were graded higher by IGI
33% were graded the same
17% were graded lower

Clarity grading:

50% were graded higher by IGI
50% were graded the same

Although the sample size is not statistically significant, it looks like you have less than a 50-50 chance of getting a correct grading by IGI (assuming GIA is correct
)
 

dimonbob

Brilliant_Rock
Trade
Joined
Dec 12, 2000
Messages
670
One out of six isn't bad for IGI. In any school I have ever attended, that is a fail mark and a note to your parents. My dad would have dropped me off a bridge somewhere if I had done that bad in school.
Thanks for putting that up.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,272
Oh my! Why doesn't this surprise me? Gary were you testing to see what would happen or did you really want 2 certs on each stone? Splendid experiment.

Rhino
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Gary
Yes on all three of our stones the true grade (AGS) was one color lower than IGI.
We where tempted by the fast delivery but where not happy with the result so went for AGS
Wayne
 

Giangi

Ideal_Rock
Joined
Jan 23, 2003
Messages
2,530
Were these stones graded by IGI NY or Antwerp??

Living in Europe, and seeing a lot of IGI and HRDs, I'll express my opinion:
IGI Antwerp isn't that bad... Nowdays is much better than 2-3 years ago... Yes, they're a bit lenient on color --even if the difference is usually not more than one grade-- but most times stricter than EGL. I find them to be very good on fancy colors grading, though. On clarity they're OK... I do use IGI Antwerp for medium-small stones, as they're inexpensive, fast and not that bad, in my opinion.

HRD is a first class lab. Simply perfect! Sometimes even too strict, in my opinion. They're VERY hard on D-E-F colors --usually HRD-'E' gets GIA-'D' and so on-- and on finish grade (= polish + symmetry)...They use loupe-clean grade that stands for flawless (if it hasn't a comment) or internally flawless, if it has a comment like 'negligible external characteristics' or 'minor graining'... They grade the clarity according to the dimensions of the inclusions, and I think (I may be wrong) that if there is a pinpoint(clear or dark) smaller than one micron, the stone gets loupe-clean rating. Someone says that if this pinpoint is black, GIA would grade the stone as VVS 1... That's the most significant difference between HRD and GIA...
 

Egon

Rough_Rock
Joined
Apr 13, 2003
Messages
18
Kind of a follow up question/comment. What kind of regulations/rules are there as
far as calibration and traceability for Sarin machines etc? Anyone follow ISO procedures? Yes, an evil thing I know, I have to deal with them myself. I would
assume that at least in the states, you would calibrate of a NIST traceable standard.
Or is it left up to the individuals how much time/money they want to put into
maintaining their equipment and traceability?
 

Yupi

Rough_Rock
Joined
Feb 8, 2003
Messages
74
So can one make the conclusion that GIA is the more widely accepted and truthworthly place ? And why isn't GIA providing more detail measurements on the diamonds ? eg. pavilion angle etc ?
 

Dana

Rough_Rock
Joined
Feb 24, 2003
Messages
10
----------------
On 4/18/2003 8
5:54 PM Cut Nut wrote:

I have just had these 6 stones submitted to two labs. The first grade on each stone is the GIA, the second is IGI.

1 1 0.96 F SI1 E SI1

2 8 0.99 H VS2 G VS1

3 19 0.96 G SI1 G SI1

4 28 0.93 G SI1 H SI1

5 43 0.98 H VS2 H VS1

6 45 0.96 H SI2 G SI1



----------------
How this reads to me , just a layman but interested in diamonds is that IGI isn't that bad at all. Please correct me if I'm wrong.....
-Dana
 

slmulkey

Shiny_Rock
Joined
Oct 30, 2002
Messages
133
Just curious...What was your assement of the 6 diamonds you listed? Was GIA 100% correct on the grading (in your opinion)?
 
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