The Laboratory Manual Harmonisation Committee (LMHC), comprising some of the important gemmological labs from across the world, at its recent meeting in Lucerne, Switzerland has reported significant progress in the harmonisation of wording on laboratory reports and the reporting of new treatments for certain gemstones.

A release issued yesterday by the Committee said that the LMHC members agreed to modify the parameters for use of the term "padparadscha” and also introduced new frameworks for reporting on organic fissure-filling in any gemstone and about hydrophane opal.

This was the 29th meeting of the body which comprised of representatives from the Central Gem Laboratory (CGL), CISGEM Laboratory, DSEF German Gem Lab, Gübelin Gem Lab, GIA Gem Laboratory, the Gem and Jewelry Institute of Thailand (GIT) and the Swiss Gemmological Institute SSEF. LMHC is not formally connected to any trade organisation.

All LMHC infosheets, including the two new releases, and the recently amended one are accessible on the new LMHC website (https://www.lmhc-gemmology.org/).

The LMHC also discussed issues raised by new treatments. These include the low-temperature heating of corundum and a new sapphire heat treatment, which has been incorrectly named High Pressure-High Temperature (HPHT) heating in the trade. Current scientific knowledge and available data from the LMHC laboratories indicates that the latter treatment is essentially a form of heating, and as such is similar to most known heating techniques. It consequently does not currently require specific reference on the laboratory reports of the LMHC members.

Nonetheless, LMHC stressed that all heat treatments may create fissures or expand pre-existing fissures in a gemstone, especially when high temperatures are applied. These could have a negative impact on the stability of the heated stone.

Additionally, during their meeting in Lucerne the LMHC members initiated a project which is aimed at harmonising the use of colour descriptions and colour trade terms at the various LMHC laboratories.

"We are very pleased to see that all laboratories represented at LMHC are constructively working together for a harmonisation on issues that are important for the trade and consumers," said Dr Lore Kiefert, host of LMHC, summarising the achievements made during the meeting in Lucerne.