The Laboratory Manual Harmonisation Committee (LMHC) announced major progress in unifying the language used in gemmological reports, following its recent meeting hosted by the Swiss Gemmological Institute – SSEF in Basel, Switzerland, in May.
At the session, members unanimously approved three new information sheets and revised the existing sheet on Fei Cui and jade terminology. These documents, which harmonise both terminology and testing protocols, are now publicly available on the LMHC website (https://www.lmhc-gemmology.org/).
LMHC brings together representatives from leading gemmological bodies, including the Central Gem Laboratory (CGL), CISGEM Laboratory, DSEF German Gem Lab, GIA, The Gem and Jewelry Institute of Thailand (GIT), Gübelin Gem Lab Ltd., and SSEF. The committee plays a pivotal role in providing the trade with scientifically grounded and standardised terminology.
Newly Released Information Sheets:
- IS No. 16: Colour Stability Testing of Gemstones (v1; Aug 2025)
Establishes a standard procedure for testing gemstone colour stability, addressing fading or colour shifts caused by prolonged daylight exposure. The test involves initial colour grading, light exposure, regrading, and optional UV activation to assess reversibility. The results are to be reported as either stable or unstable. - IS No. 14: Cobalt Spinel (v1; May 2025)
Defines cobalt spinel as a Mg-Al spinel whose blue colour originates mainly from cobalt absorption bands. Stones treated with cobalt diffusion or glass infilling do not qualify. The sheet also differentiates cobalt spinel from iron-coloured blue spinel. - IS No. 15: Tanzanite (v1; May 2025)
Standardises terminology for tanzanite, identifying it as the vanadium-bearing blue to purple variety of zoisite. The sheet highlights its strong pleochroism and notes that heat treatment, often undetectable, enhances colour by removing the yellow-brown component.
Updated Information Sheet:
- IS No. 11: Jade and Related Materials (v5; May 2025)
Clarifies the scope of “jade” to include aggregates composed mainly of jadeite, omphacite, kosmochlor, or nephrite. It also introduces standard definitions for “Fei Cui” (翡翠), describing it as an ornamental aggregate primarily made of jadeite, omphacite, and/or kosmochlor, widely used in Asian trade terminology.
Dr. Michael S. Krzemnicki, Director of SSEF, remarked, “It is encouraging to see all LMHC member laboratories working collaboratively to harmonise terminology on issues crucial to transparency and consistency in gemmological reporting. These new and updated information sheets tackle key disclosure challenges.”