I would rate them equally, with the proviso that Guebelin is mostly used for important stones (particularly for an assessment of whether colour origin is natural or not) and is not as well known as GIA.

I want to add that I think I would represent an average consumer when it comes to jewelry and I have never heard of this lab.  I have known David for a few years and I trust him, if he presented me with a stone from this lab and explained what it was I would believe him because of the relationship we have.  However, if I was just shopping around for a colored diamond and a vendor showed me a stone with that cert I would definitely hesitate because I have never heard of it before.  I think that when it comes to most people that staying with something familiar is important especially when they could be a new customer who doesn't really have a relationship with the vendor yet. 

I've heard of Gubelin but I couldn't tell you where I heard about them.  Maybe from a Sotheby's auction ad?  Regardless, people go with what they're most comfortable with, particularly when GIA is based in the US and Gubelin is located in Switzerland.

Mikla

When Soteby's or Christie's do the "Fine Jewelry Auctions", the Top Lots have specified in the catalogue "GÜBELIN certificate".
The last important fancy diamonds, as "The Vivid Pink" and the Vivid Blue 7.03ct, had this reference.

The certificate costs are very high. Under 3 carats, the price ranges from $ 317 base + $ 86 for Clarity granding + $ 220 for Low-temperature analysis + $ 182 for Gemologist notes and determination for authenticity and treatments. 



Thanks 

As more of an average consumer, I would probably walk away from a Gubelin-certified stone. From everything I've learned so far, I wouldn't buy a diamond unless it was GIA-certified. The fact that they have the best reputation in the industry for their accuracy and strictness in grading is reason enough for me not to risk going with another lab--especially if I ever wanted to re-sell it!

I can totally understand where ellie is coming from- I would have a lot of trepidation buying a high dollar stone without the GIA report.
Even one grade difference can make a HUGE difference in the price.
We are considering a few 2ct plus stones right now that lack GIA reports- but they are VERY well priced- and we will likely submit them to GIA if we buy them.....

I would not only hesitate- I'd stop. I would not buy a high dollar stone without the GIA.
If it had GIA and Gubelin, fine- maybe it's my NY diamond dealer roots, but I need to see a GIA report to feel comfortable with the color.
Furthermore, I don't recall seeing any cutter or dealer presenting mega dollar stones with a Guberlin.
So I'd have to advise consumers to do the same- based on my own feelings and experience.

ETA- Since OMC is in Europe, it's quite likely he'd have different preferences....

Okay. You two intellectuals are confusing me. What is a Gubelin? Is it a super diamond grading company? I confess I have never heard of it. Even after being on this forum for a few years, I still find I have things to learn about diamonds..........

But what about colored diamonds? Or do they specialize in sapphires, rubies, etc...

I'll weigh-in and say that I think one would be making a safe purchase with a Gubelin report. AS OMC wrote, they began as an in-house lab dedicated to assuring that the stones in their own jewelry pieces were what they said they were. Over time, the lab earned a reputation for reliable and well-regarded work with fine colored stones and it branched out to include gems submitted by others. I don't think the lab is as well-known in the US as it is in Europe, most likely due to its location. However, I do think it is generally highly regarded by jewelry industry insiders... perhaps less so in the very tight diamond business... I don't know. I see David's point. Anyway, as others wrote, you usually see Gubelin reports here and there for high-end jewelry pieces, especially at big auction houses (the question as to whether or not prices are completely inflated for high-end jewels at big-name auction houses is another matter entirely...).

Another way to look at it: Right or wrong, I've always thought about Gubelin when it involves high-end jewelry PIECES and GIA when it is about individual, high-end jewelry STONES.