GIA (Gemological Institute of America) is a well-known and respected school and gemological lab with offices and branches around the world. They established the science of gem and diamond grading and were the first institution in the world to attempt to formalize pearl grading.
And they still have a long way to go. While the GIA remains foremost, resources and staff are limited, especially when compared to identification of other gems. We scarcely see most certificates, but I'm certain a lot of "undetermined origin" reports are issued by the GIA. Location of harvest and species are infinitely difficult to to establish in the absence tangible provenance and established baseline data.
However, those are a far cry better than erroneous reports, which are often solely meant to add value and little else.
A lab must have known exemplars and analogs on file for identification, namely pearls from known harvest grounds (ie) Persian Gulf, South Sea, Indo-China, Japan, Pacific Islands and Sea of Cortez. In the absence of these, identifying rare species are near to impossible.
Even at best, subjective conclusions may be drawn. Until all gem labs come up with a universal system that employs objective methods used in pathological and forensic sciences, reputable lab reports may be overshadowed by dubious claims from other labs. These are not limited to incidental harvests (namely keishi or spontaneous farm reared pearls) or other pearls from other regions with similar growth and structural patterns. Likewise no consideration is made for unsustainable or endangered harvests, (ie) Tridacna and Strombus. Shells or meat of those are strictly regulated by CITES and/or other laws governing trade in endangered animal parts, but many pearls slip through the cracks and are openly traded without adequate documentation as to origin.
A lab report, even from the most reputable service
must never stand alone as to value. I can't say it enough. Unless you know your source, you'll never know for sure.
