LMHC: Progress On Harmonization Of Color Description, New Treatment Issues

(IDEX Online) – Significant achievements in the harmonization of wording on laboratory reports and the reporting of new treatments were reached during the 29th meeting of the Laboratory Manual Harmonisation Committee (LMHC), which was recently hosted by the Gübelin Gem Lab in Lucerne, Switzerland.

The LMHC is currently 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. The organization is not formally connected to any trade body.

During the meeting, the LMHC members agreed to modify infosheet No. 4, concerning the use of the term "padparadscha." The infosheet now specifies that the term is not applicable if the color of the stone is unstable and shifts to pink when exposed to a color stability test. Additionally, a new infosheet about organic fissure-filling in any gemstone (IS No. 12) and an infosheet about hydrophane opal (IS No. 13) were unanimously approved by the laboratory representatives.

All LMHC infosheets, including the two new releases, 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 stresses 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.

LMHC members also initiated a project aimed at harmonizing the use of color descriptions and color 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 harmonization on issues that are important for the trade and consumers," said Dr Lore Kiefert, host of LMHC, summarizing the achievements made during the meeting in Lucerne.

Pictured above: Sapphires heated with a new heating process, incorrectly named High Pressure-High Temperature (HPHT) heating in the trade.