Gemstone Grading

In the last two decades there has been a proliferation of certification, not only for diamonds but for gemstones as well. There are a number of reputable laboratories which grade and provide reports on gemstones.

• Gemological Institute of America (GIA), the main provider of education services and diamond grading reports
• American Gemological Society (AGS) is not as widely recognized nor as old as the GIA but has a high reputation.
• American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA) the largest trade organization of jewelers and dealers of colored stones
• American Gemological Laboratories (AGL) which was recently taken over by “Collector’s Universe” a NASDAQ listed company which specializes in certification of many collectables such as coins and stamps
• European Gemological Laboratory (EGL).
• Gemological Association of All Japan (GAAJ), aka Zenhokyo, the preferred lab within Japan, also very active in the gemological research
• Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University, and has a good reputation for their gemmological research
• Asian Institute of Gemmological Sciences (AIGS), the oldest gemological institute in South East Asia, involved in gemological education and gem testing
• Swiss Gemmological Institute (SSEF), founded by Prof. Henry Hänni, offering a high scientific standard, and focusing on coloured gemstones and the identification of natural pearls
• Gübelin Gem Lab, the traditional Swiss lab founded by the famous Dr. Eduard Gübelin. Their reports are widely considered as the ultimate judgement on high-end pearls, coloured gemstones and diamonds

Each laboratory has its own methodology to evaluate gemstones. Consequently a stone can be called “pink” by one lab while another lab calls it “Padparadscha”. One lab can conclude a stone is untreated, while another lab concludes that it is heat treated. To minimise such differences, seven of the most respected labs, i.e. AGTA-GTL (New York), CISGEM (Milano), GAAJ (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), aiming at the standardisation of wording on reports and certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to find agreement on due to the constant discovery of new locations. Moreover determining a “country of origin” is much more difficult than determining other aspects of a gem (such as cut, clarity etc.)

Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate. One such example is to make use of the differences in country of origin: a sapphire from Kashmir, India (celebrated for its cornflower blue color) commands four times the price of the same stone from Sri Lanka and twice the price as a similar stone from Burma.

Enamelled gold, amethyst and pearl pendant, about 1880, Pasquale Novissimo,, born 1844 – died 1914 V&A Museum number M.36-1928