Blue Nile Girdle Classification and AGS cert doesn''t match up?

[singular]

Can someone shed some light on why Blue Nile''s Girdle Classifications consider girdles thicker than it should as compared to Whiteflash''s chart (http://www.whiteflash.com/diamonds_info/t/articles.aspx?articleid=134&zoneid=5)?

For example.
http://www.bluenile.com/diamonds_details.asp?__fun_frm=i&track=view_details_btn&elem=img&pid=LD00294935&filter_id=0
Bluenile: Thin to Slighly Thick
Cert: 1 to 1.9 %
WF Chart: Thin

http://www.bluenile.com/diamonds_details.asp?__fun_frm=i&track=view_details_btn&elem=img&pid=LD01162320&filter_id=0
Bluenile: Medium to Thick
Cert: 1.3 to 3.5%
WF Chart: Thin to Medium

http://www.bluenile.com/diamonds_details.asp?__fun_frm=i&track=view_details_btn&elem=img&pid=LD01107375&filter_id=0
Bluenile: Slightly Thick to Very Thick
Cert. 1.8 to 4.3%
WF Chart: Thin to Slightly Thick

 

[JohnQuixote]

Welcome to PS singular.

GIA and AGS treat girdle measurements differently. GIA measures at the 16 thinnest positions. AGS measured thinnest and thickest places everywhere along the girdle. This means AGS ranges will seem wider than GIA's.

My understanding is that BN applies GIA's system to all their reports, thus the discrepancy. One poster here - screen name WorkingHardForSmallRewards - wrote about this some time ago - I'll try to find it. [ Edited to add: Here is the post that answers your question. ] On BN's site you should be safe if you apply the AGS chart you linked to AGS-graded diamonds and use their assessment for GIA graded diamonds.

Also, here is a thread with more info and illustrations about the exciting world of girdles.

 

[WorkingHardforSmallRewards]

Yea I called and spoke with them about that a long time ago now. At first they told me that they couldn't find any information about a change in girdle measurements and that the diamond I was looking at had a very thick girdle--one guy said that that was a potential problem and he normally wouldn't recommend diamonds with Thick girdles, but that it seemed to be ok in this one (meaning that they MUST be losing sales because of this silly problem) .

Then they told me they spoke with someone from AGS who supposedly worked for them? he said that there was no mistake on the site and ignored my concerns. I called AGS myself and eventually spoke with some members of their lab, confirming BN was wrong, then, after a couple emails with examples, wouldn't you know, BN ended up referring me to pricescope to the chart that JQ provided years ago and said they would look into it more but that so far that was the only such chart they could locate. Eventually I called back one more time with a few more examples, honestly I just didnt want them to loose any sales or credibility just because they cant get the information right on there website...and then one of their gemologist had a revelation and pointed out that a diamond couldn't have a Thick or Very thick girdle AND and AGS0 (which I had mentioned to them about 3 times already) so eventually they discovered I was right and changed a couple of the diamonds and told me to feel free to email them if I ever found any others with such mistakes. It seems they are insistent on discovering things themselves instead of considering what other people have to say...anyway It was pretty fun from my end as I was really just trying to help out, but they wouldn't have any of it.