Diamond Mirror

Blue to purple spinel including coloured predominately by cobalt (left), iron (right) and a combination of both elements (middle).

Holding its 31st meeting in Basel, Switzerland, in May 2025, the Laboratory Manual Harmonisation Committee (LMHC) has reported notable progress in the harmonisation of treatment disclosure on laboratory reports and gemstone nomenclature. LMHC was originally formed in 2001, bringing together 7 major international gemmological laboratories based in America, Asia and Europe.

The LMHC is currently comprised of representatives from the Central Gem Laboratory (CGL), CISGEM Laboratory, DSEF German Gem Lab, Gübelin Gem Lab (GGL), GIA Gem Laboratory, the Gem and Jewelry Institute of Thailand (GIT) and the Swiss Gemmological Institute SSEF. The organisation is not formally connected to any trade organisation.

During the recent meeting in May 2025 hosted by the Swiss Gemmological Institute SSEF, the members of LMHC agreed to slight modifications on a number of their information sheets, which exist to facilitate better communication and understanding among professionals in the industry and which are publicly accessible on the LMHC website since many years.

In addition, the LMHC members discussed recent issues in the trade and agreed to add new information sheets that focus mainly on gemstone nomenclature and testing protocols, to be taken as guidelines for both gemmological laboratories and the gem trade. These new information sheets will include a harmonized protocol for colour stability testing (of corundum), and information sheets concerning the nomenclature of tanzanite vs. zoisite, cobalt-spinel, and emerald vs. green beryl. The amended and the new information sheets will be published in the coming weeks on the LMHC website.

“This meeting has been very productive. All laboratories represented at LMHC worked in a very constructive atmosphere to agree on harmonized language and guidelines to ensure greater consistency and clarity in gemmological lab reports for the gem trade.” said Dr Michael S. Krzemnicki, host of LMHC, summarising the progress made during the meeting in Basel.

All LMHC information sheets are accessible on the LMHC website (https://www.lmhc-gemmology.org/). The revised versions including new information sheets as agreed in this meeting will be uploaded in the coming weeks.


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Lab Meeting (LMHC) Makes Further Progress in Harmonization of Treatment Disclosure and Gemstone Nomenclature Blue to purple spinel including coloured predominately by cobalt (left), iron (right) and a combination of both elements (middle). Holding its 31st meeting in Basel, Switzerland, in May 2025, the Laboratory Manual Harmonisation Committee (LMHC) has reported notable progress in the harmonisation of treatment disclosure on laboratory reports and gemstone nomenclature. LMHC was originally formed in 2001, bringing together 7 major international gemmological laboratories based in America, Asia and Europe. The LMHC is currently comprised of representatives from the Central Gem Laboratory (CGL), CISGEM Laboratory, DSEF German Gem Lab, Gübelin Gem Lab (GGL), GIA Gem Laboratory, the Gem and Jewelry Institute of Thailand (GIT) and the Swiss Gemmological Institute SSEF. The organisation is not formally connected to any trade organisation. During the recent meeting in May 2025 hosted by the Swiss Gemmological Institute SSEF, the members of LMHC agreed to slight modifications on a number of their information sheets, which exist to facilitate better communication and understanding among professionals in the industry and which are publicly accessible on the LMHC website since many years. In addition, the LMHC members discussed recent issues in the trade and agreed to add new information sheets that focus mainly on gemstone nomenclature and testing protocols, to be taken as guidelines for both gemmological laboratories and the gem trade. These new information sheets will include a harmonized protocol for colour stability testing (of corundum), and information sheets concerning the nomenclature of tanzanite vs. zoisite, cobalt-spinel, and emerald vs. green beryl. The amended and the new information sheets will be published in the coming weeks on the LMHC website. “This meeting has been very productive. All laboratories represented at LMHC worked in a very constructive atmosphere to agree on harmonized language and guidelines to ensure greater consistency and clarity in gemmological lab reports for the gem trade.” said Dr Michael S. Krzemnicki, host of LMHC, summarising the progress made during the meeting in Basel. All LMHC information sheets are accessible on the LMHC website (https://www.lmhc-gemmology.org/). The revised versions including new information sheets as agreed in this meeting will be uploaded in the coming weeks.