The Laboratory Manual Harmonisation Committee (LMHC) recently held its 30th meeting in Basel, Switzerland, where the participants reported significant progress in the harmonisation of language used in laboratory reports. LMHC, which comprised representatives from major gem labs such as the GIA, CISGEM, and Gübelin Gem Lab, also discussed the challenges faced in detecting corundum treatments, specifically low-temperature heating and irradiation.

Rubies and pink sapphires that have undergone low-temperature heating have increasingly appeared in the market to slightly shift their colour to a more desirable hue. On the other hand, some have undergone radiotherapy treatment, typically used for cancer patients, which induces a shift in the colour centre to a more attractive shade.

The LMHC labs decided to conduct further research on these corundum treatments to establish harmonised criteria for detecting their use. Dr Michael S. Krzemnicki, host of the LMHC meeting, expressed satisfaction with the progress made, stating that the harmonisation efforts were necessary for consistency and clarity in gemmological lab reports.

The Swiss Gemmological Institute SSEF hosted the two-day meeting on 5-6 December, 2022, with no formal connections to any trade association. The LMHC continues to work towards achieving global harmonisation and standardisation in laboratory reports for the gem and jewellery industry.

Photo: Heated pink sapphire with a characteristic FTIR spectrum. © LMHC