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GIA report differs from Sarin (repost, but with new info)... please help

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golfer

Shiny_Rock
Joined
Oct 7, 2002
Messages
128
I just bought a diamond online, should be at least a week before I actually get it in hand and have it appraised.

Here's my concern.

GIA report says:
Depth 60.3
Table 56
Culet None
Girdle Thin to medium
Meas: 7.57 - 7.58 x 4.57

Sarin says:

Depth 60.2 (slightly off)
Table 56.9 (the same whole #)
Culet .4% V. small
Girdle 1.2 % (is that than to medium?)
Meas: 7.50 - 7.54 x 4.53 (all three are different!)

What are the chances somebody has shown me GIA and Sarin for two different stones? Reputable internet dealer, but who knows what someone (their wholesaler) is telling them...

Any thoughts?

Are these just normal variations b/w Sarin and GIA?
 

golfer

Shiny_Rock
Joined
Oct 7, 2002
Messages
128
Relatedly... if this is the same stone, which is likely more accurate, GIA or Sarin?
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
Golfer,

can you post the complete information you got form the GIA & Sarin reports, incl. angles and 3 digit carat weight. As far as I can see, slight differences between GIA and Sarin are normal. But it is hard to tell if you don't post all the information you have.

Scotch
 

golfer

Shiny_Rock
Joined
Oct 7, 2002
Messages
128
Scotch,

Thanks for your reply.

GIA:
Weight 1.57
Depth: 60.3
Table: 56
Girdle: Thin to Med.
Culet: None
Meas: 7.57 - 7.58 x 4.57

Sarin:
weight: 1.572
diam: 7.52 (7.50 - 7.54) x 4.53
depth: 60.2%
crown: 34.2 / 15.2%
pavil: 40.9 / 42.6
table: 4.28 mm 56.9%
culet: .4% v. small
girlde: 1.2% (1.0 - 1.6)%

Any thoughts?
 

golfer

Shiny_Rock
Joined
Oct 7, 2002
Messages
128
Actually I edited it (adding carat weight) right after posting, so we probably just got crossed.
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
From my limited experience, while some differences between GIA and Sarin appear to be normal, they are often limited to things like GIA finding no culet and Sarin listing a small culet between 0.4% - 0.6%. I don't think the kind of differences you have there are normal. Assuming e.g. that the angles are as listed by Sarin, the difference in dimension would amount to ca. 3 carat weight difference. You may definitely want to go back and try to get verification from whoever provided you with that info.

Regards,
Scotch
 

golfer

Shiny_Rock
Joined
Oct 7, 2002
Messages
128
"Assuming e.g. that the angles are as listed by Sarin, the difference in dimension would amount to ca. 3 carat weight difference."
----------------



I'm not exactly sure what you mean by that. The angles are not on the GIA report, and there is no weight difference on the two reports (1.57 vs. 1.572). Can you please explain?
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
If the proportions are as Sarin says, given the GIA dimensions the stone should be about 3 ct heavier than it is. If the GIA dimension are correct, the Sarin angles can't be right. What I'm saying is that something doesn't make sense there, and you may want to go back to the source of the information and get it sorted out.

Scotch
 

dannanews

Rough_Rock
Joined
Oct 8, 2002
Messages
9
I found a dealer who was willing to do a Sarin report for me on a stone I bought elsewhere. He did me a favor, which was really cool. Definintely a good way for him to attract future business.

Anyway, I have the same experience. The Sarin report is different than the GIA report. I'm not too concerned because I'm happy with the stone. Here are the specs:

GIA
Round Brilliant
1.50 carat
7.40-7.45 x 4.50 mm
Depth: 60.6 %
Table: 59 % !!!!!
Girdle: Very Thin - Medium, faceted
Culet: None

Polish: Good
Symmetry: Very Good
Clarity: VS1
Color: F
Flourescense: none

Sarin
Round
1.50 carat
7.42 (7.40-7.44) x 4.50 mm
Depth: 60.6%
Table: 60.5% !!!!!
Girdle: 0.7 - 1.9
Culet: 1.0 %

Crown Angle: 34.0 degrees
Crown Height: 13.5 %
Pavil Angle: 41.0 degrees
Pavil Depth: 43.4 %
(NO clarity, color, and Flour. as they are subjective, but he guessed at: VS1, G, none)

What I find amazing is the difference in table. I'm not sure if I would have been more or less interested in this stone if I had the Sarin report before hand.

I ran the numbers through the HCA and got 1.6 using the crown/pavil degrees and got 3.2 using the crown/pavil %. That concerns me more. I am quite happy with a 1.6 from HCA but not 3.2. I would not have bought a 3.2. After looking through the stone with a Ideal-Scope I would have guessed it to be around 2.0.

Like I said, I am very happy with the stone. I could have probably gotten a stone that would have had more light return, but I'm not convinced that I would have been able to tell the difference with the naked eye.

It would be interesting to hear from some experts here what they think of the difference in this report.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,271
Hi golfer & danna,

I get to see these things quite often. There can be a number of different reasons for the variations between the 2. One can simply be the calibration of the Sarin measuring the stone. I happen to have both Sarin BrilliantEye and OGI MegaScope in our store and find that the OGI gives me more precise measurements. Also I have calibrated it myself against AGS certed stones that I've meticulously measured manually. Back when I was carrying a certain brand that offered MegaScope data, quite frequently I would get asked why my MegaScope data differed so much from the suppliers and I believe the answer is in the calibration. You can check this by verifying how accurate the information on the report is to that of the stone being measured. Things like comparing the estimated weight with the actual weight of the diamond & the diameter and depth measurements which are definite will give you an idea usually how well the instrument is calibrated. However keep in mind that labs do make mistakes too.

From what I know GIA still measures tables manually. I may be wrong about this as I don't keep a tab on how they're doing that but one thing I do know is that both GIA and AGS round up or round down the table measurement. Take for example this diamond which according to the MegaScope has a 56.4% table. GIA rounds it to an even 56%. http://www.goodoldgold.com/1_01ct_e_vs2_h&a.htm If you page through most of the stones on our website you'll see that the table measurement by the lab is in line with the MegaScope measurements from stone to stone with very few exceptions.

But guess what ... if GIA's manual measurement came to 56.7 they would have rounded it up to 57% and that person's Sarin (whose calibration may possibly be off) measures the stone at 56.1 and the diamond seemingly is off by a full 1% in the table measurement when in fact the difference can be less than a half degree.

Here's another example in which the MegaScope reports a 55.8% table (which you'd think GIA would just say 56% but instead they report a 55% table. Their manual measurement may have been 55.4% whereas the MegaScope was 55.8 and the real difference is only .4% http://www.goodoldgold.com/1_04ct_g_vvs2_h&a.htm

In looking at your stone inparticular.

GIA: Weight 1.57
Sarin: weight: 1.572

No big woop.

GIA: Depth: 60.3
Sarin: depth: 60.2%

Also no big woop.

GIA: Table: 56
Sarin: table: 4.28 mm 56.9%

Considering GIA rounds their measurement this may seem closer than we think. (My examples above).

GIA: Girdle: Thin to Med.
Sarin: girlde: 1.2% (1.0 - 1.6)%

Right on.

GIA: Culet: None
Sarin: culet: .4% v. small

Sarin BrilliantEye's are off on their culet measurements so if GIA says none I'd believe it was none.

GIA: Meas: 7.57 - 7.58 x 4.57
Sarin: diam: 7.52 (7.50 - 7.54) x 4.53

This seems to be the biggest discrepancy and may be due to the calibration of the unit. I'd have to see the stone physically to say for sure.

crown: 34.2 / 15.2%
pavil: 40.9 / 42.6

GIA doesn't give this so you're trusting the measurements of the machine using it.

There's my .02c

Hope that helps.

Kind regards,
Rhino
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Rhino's dead on. Don't worry about the small discrepancies. It's the difference between a man measuring the diamond and a machine measuring the diamond.

I get the biggest kick out of the fact that the man usually beats the machine.

Rich, GG
Sarasota Gemological Laboratory
 
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