What are your gem lab preferences, and why?

[kenny]

For grading of D-Z diamond cut, I strongly prefer AGS over GIA; GIA's Excellent cut grade is too loosey goosey.
For D-Z diamond grading of clarity and color I consider AGS or GIA close enough to have no preference.
For fully natural Fancy Colored Diamonds - GIA only.
For non-diamond Colored Stones - AGS only.

If the grading report is older than ... say ... 2 years, I'd want it sent back for a fresh report.

I'd never buy a stone that was too inexpensive for the seller to bother sending it to any lab, IOW vendor-graded.
I'd also never buy a stone that the seller sent to a second-tier lab; I'd worry they felt the stone needed "flattering" grading to sell. No thanks.

What say you?

 

[DejaWiz]

For grading of D-Z diamond cut, I strongly prefer AGS over GIA; GIA's Excellent cut grade is too loosey goosey.
For D-Z diamond grading of clarity and color I consider AGS or GIA close enough to have no preference.
For fully natural Fancy Colored Diamonds - GIA only.
For non-diamond Colored Stones - AGS only.

If the grading report is older than ... say ... 2 years, I'd want it sent back for a fresh report.

I'd never buy a stone that was too inexpensive for the seller to bother sending it to any lab, IOW vendor-graded.
I'd also never buy a stone that the seller sent to a second-tier lab; I'd worry they felt the stone needed "flattering" grading to sell. No thanks.

What say you?

Agree on all sentiments, and would add GCAL 8X to my list of preferred/trusted type/style of grading reports.

 

[AllAboardTheBlingTrain]

Personally, I prefer a GIA report for diamonds, with HRD a possible second option (don’t live in the US, HRD is well regarded where I live, but of course I prefer GIA). This is for diamonds. I have never bought a non-diamond gemstone with a report because I don’t really have any of considerable enough size or value to bother.

 

[max1111]

For D-Z diamond grading of clarity and color I consider AGS or GIA close enough to have no preference.

Did you see my thread?

 

[kenny]

Did you see my thread?

Better yet, I've seen all 83 zillion AGS/GIA comparison threads posted over the last 20 years here on Pricescope.
My opinion is based on those threads, not any one thread reporting the odd high or low grade from a lab.
I've also read about sending the exact same diamond to a lab more than once and it coming back with a different grade.

Hence my OP.

 

[max1111]

Better yet, I've seen all 83 zillion AGS/GIA comparison threads posted over the last 20 years here on Pricescope.
My opinion is based on those threads, not any one thread reporting the odd high or low grade from a lab.
I've also read about sending the exact same diamond to a lab more than once and it coming back with a different grade.

Hence my OP.

Just wondering if you missed the bit where myself and at least one other person combed through 60+ triple certified stones. Bit more than the odd high or low grade.

Anyway to answer the OP.

I would not trust AGS alone for colour grade. 40% of stones overgraded vs GIA in the only collection of triple certified stones online.

 

[Karl_K]

I good with AGS or GIA for rounds for the most part.
For fancies I lean a bit more towards AGS for being more consistent in some cases but GIA is ok also.
GCAL 8x grading report is growing on me.
For lab diamonds it is a very nice report.
For mined diamonds with the higher prices it does not have enough history yet for me to back it strongly.
edit: the closed nature of some of the tests and the theory behind them harms the credibility of the 8x report for me.
All that said if Im paying the huge D/IF or D/FL premium then GIA would be my only acceptable lab report.
For fancy colored diamonds that is true also, GIA only.

 

[etudes]

For diamond above 0.3ct : GIA (I don't live in US. I've never seen AGS graded stones here so far, although I won't say no)
For diamond lower than 0.3ct : I'm okay with vendor graded
For colored diamond (fancy and lower D-Z range) : GIA
For other colored stones : no preference, but I never buy expensive CS anyway. If I pull the trigger for good quality/expensive jade, probably Nanyang Gemological Institute.