This content was first published on IGR – Italian Gemological Review no. 12 in 2021. The information provided here is therefore current as of the original publication date.
Since 2017, in the Panjshir Valley in Afghanistan, a new emerald with features diverging from the gemstones that has been previously cultivated in the area is being mined. It is much more similar to emeralds of Colombian provenance. A recent study, carried out by Dr. Krzemnicki of the Institute SSEF and Dr. Wang and Dr. Büche of the University of Basel, has mapped out what are the differences and similarities between these “new” emeralds and other ones available on the market. The research was conducted through examination of 113 specimens ranging in size from 1 to 30 carats. 54 of these pieces belong to the new type called “Panjshir Type II”. To achieve this distinction, numerous tests of various kinds were carried out. Among these, the typical gemological ones have shown that type II emeralds have a refractive index of 1.575–1.582 and a density of 2.72, lower values than the other Afghan samples and more similar to the more distant Colombian siblings.
A careful microscopic study has revealed a very transparent material with almost no inclusions except occasional zoning, fluid inclusions of several different shapes and channels parallel to the C axis filled with iron (Fe) hydroxides. It is precisely iron that proves to be the key element for differentiating the two qualities, being absent in the Colombian samples while it generates in the Afghan samples that were tested a weak peak at 830 nm within the absorption spectrum (UV- Vis-NIR).
Among the investigations carried out by the group, the data for iron, vanadium and chromium obtained through LA-ICP-TOF-MS were plotted in a diagram correlating Fe with the ratio of V to Cr. From this diagram it can be seen very clearly that the samples of Afghan origin all have higher ppm iron values, including those belonging to type II. Through the combination of classical gemological techniques with advanced analytical methods, the research, to date the most detailed and exhaustive, has provided surprisingly useful information for the identification of a product that on the market is considered a competitor to what is currently the most valuable and appreciated variety of emerald. The work is available online, for further information on SSEF and Gem-A websites.
Gem News published on IGR – Italian Gemological Review #12, Summer 2021
