Inside Facette: Low Heat, New Lightbox, and so much more!
Gary Roskin –
Roskin Gem News Report –
Leading the Swiss Gemmological Institute SSEF’s 2024 Facette magazine (FREE Download here) is the feature Low-Temperature Heating of Corundum: Possibilities and Challenges for Detection.
The article gives a nice overview of past treatments, but then quickly examines the success of a new discovery using Raman Spectroscopy that has led to very promising detection results.
“Heat treatment is generally applied to gemstones to change and enhance their colour. Over the past few decades, it has become a very common practice for certain gem species and varieties, such as aquamarine, amethyst (resulting in citrine), copper-bearing tourmalines (Paraiba), tanzanite, and notably for any colour variety of corundum.”
The article does go on to mention the historic heat treatment of gems, specifically referencing the effect of heating rubies.
To the Point – Heat Affects Diaspore and Goethite Inclusions
The focus of this feature points to the testing of inclusions that appear to be affected by low temperature heat, mainly diaspore and goethite. “The study, entitled Dehydration of Diaspore and Goethite during Low-Temperature Heating as Criterion to Separate Unheated from Heated Rubies and Sapphires using a Raman microprobe and their phase transformation and dehydration to corundum and hematite could be clearly documented in all samples.
In conclusion, SSEF says that “Raman spectroscopy has proven to be a very useful analytical method to document these phase transformations and can thus be considered a very promising tool to separate unheated from heated gem-quality ruby and other corundum varieties and even other gemstones.”
We are looking forward to hearing more on this.
MORE:
There are SO many great articles in here … from the color range of Paraiba tourmaline, some good info (and a sales pitch) for a new standardized light box, and a history of a René Boivin 1944 brooch by Kathia Pinckernelle, M.Phil. FGA. Jewellery Historian and Curator
of SSEF’s Jewellery Collection. Fascinating!
