Gemstone - Grading

Grading

There are a number of laboratories which grade and provide reports on gemstones.

• International Gemological Institute (IGI), independent laboratory for grading and evaluation of diamonds, jewelry and colored stones.
• Gemological Institute of America (GIA), the main provider of education services and diamond grading reports.
• Hoge Raad voor Diamant (HRD Antwerp), The Diamond High Council, Belgium is one of Europe's oldest laboratories. Its main stakeholder is the Antwerp World Diamond Centre.
• American Gemological Society (AGS) is not as widely recognized nor as old as the GIA.
• American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA), a trade organization of jewelers and dealers of colored stones.
• American Gemological Laboratories (AGL), owned by Christopher P. Smith.
• European Gemological Laboratory (EGL), founded in 1974 by Guy Margel in Belgium.
• Gemmological Association of All Japan (GAAJ-ZENHOKYO), Zenhokyo, Japan, active in gemological research.
• Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University
• Gemmology Institute of Southern Africa, Africa's premium gem laboratory.
• 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 Henry Hänni, focusing on colored gemstones and the identification of natural pearls.
• Gübelin Gem Lab, the traditional Swiss lab founded by Eduard Gübelin.

Each laboratory has its own methodology to evaluate gemstones. 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 might conclude that it is heat-treated. To minimise such differences, seven of the most respected labs, AGTA-GTL (New York), CISGEM (Milano), GAAJ-ZENHOKYO (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), for the standardization of wording reports, promotion of certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to determine, due to the constant discovery of new source locations. Determining a "country of origin" is thus 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.