CIBJO Releases Gemmological Special Report

With less than two weeks to go to the opening of the 2013 CIBJO Congress in Tel Aviv on May 7, 2013, the sixth of the CIBJO commissions' Special Reports has been released.

Prepared by the CIBJO Gemmological Commission, headed by Hanco Zwaan, the report discusses the often difficult task of collecting and collating information on technical issues, and then communicating it in ways that are understandable to a more general audience.

In particular, the report considers dilemmas associated with properly describing treated gemstones. Concerning red andesine, a variety of feldspar, it notes that the cost of proving that a stone it is not colour treated is restrictively high, and the methods that are used are destructive. Since most of the materials in the market are most probably treated, lab reports issued for red andesine gems should state that the authenticity of their colour is not determinable.

The report also discusses the recommendation of the Laboratory Manual Harmonisation Committee that an additional category of "manufactured product" be provided to define glass-filled rubies in which the glass filling actually acts to hold the stone together.