Difficulties of colour harmonisation at heart of Gemmological Commission’s meeting

The two major issues discussed by the Gemmological Commission at the CIBJO Congress in Moscow were how gem labs worldwide can work together and harmonise nomenclature, standards and methodology to improve consistency and reliability of information to ensure consumer confidence, and the use of colour descriptive terms such as pigeon-blood red and royal blue on gemstone reports.

Ken Scarratt told the meeting that although he had originally been sceptical about the whole issue of the pigeon-blood red colour, GIA had consulted with traders and dealers around the world and examined their rubies to see if the colour was universally accepted and recognised.

With that being the case, the GIA decided to create the pigeon-blood red category.

Other participants warned of the dangers of trying to create a universally accepted definition of the pigeon-blood red colour, among them Ronnie Bauer from Australia. It was noted that market demand had pushed the gemstone industry to accept the colour definition in the same way that it had spurred the trade to provide country of origin information. Traders and sellers are also using the royal blue definition for a range of blue colour sapphires, the meeting heard.

On the issue of colour standards and definitions, Pornsawat Wathanakul of the Gem and Jewellery Institute of Thailand (GIT), also a Commission Vice President, talked about the GIT’s master sets for rubies and sapphires. She spoke about the difficulties gem labs face in setting colour standards.

Gemmological Commission President Hanco Zwaan confirmed that the issue of colour standards was a critical one, saying that the presentation illustrated the difficulties labs faced in attempting to describe colours precisely.

A second presentations at the meeting, presented by Commission Vice President Claudio Milisenda, was on the subject of opals from Ethiopia and how they could change colour simply by being immersed in water – in some cases for as little as two minutes.

Hydrophane Wollo stones revert to their original color 25 minutes after being removed from water, Mr. Milisenda explained. Opals from Ethiopia, he added, have a tendency to display surface cracks.

Photo Caption: CIBJO Gemmological Commission Vice President Claudio Milisenda describing opals from Ethiopia.