The 7th European Gemmological Symposium took place in Idar-Oberstein (Germany)on May 25 and 26, 2019. At first the opening ceremony took place with the speeches of Dr. Thomas Lind, President of the German Gemmological Association (DGemG), of Mr. Frank Frùhauf, Lord Mayor of Idar-Oberstein and Patron of the symposium, and of Dr. Gaetano Cavalieri, President of the CIBJO, the World Jewellery Confederation.
The first lecture was given by Dr. Hans-Jùrgen Henn from Idar-Oberstein, and its subject was named “A Gem Of A Life
”. In his lecture he related about his mining adventures all over the world.
The speech of Dr. James Shigley of the Gemmological Institute of America (GIA) – Carlsbad CA (USA) was named “Identifying Synthetic Diamonds: Past Progress and Current Challenges
”. In his lecture he related about historical and current methods for creating diamonds in a laboratory, and analysis methods to distinguish them from the natural ones, including spectroscopy. The commonest methods used nowadays to produce synthetic diamonds are Chemical Vapour Deposition (CVD) and High Pressure High Temperature (HPHT).
The lecture of Dr. Branko Deljanin of the Swiss-Canadian Gemlab – Vancouver (Canada) was named “Origin of Pink Diamonds: Argyle and Non-Argyle Natural, Treated and Lab-Grown
”. Argyle is a very important locality in Australia, pink diamonds were found for the first time there. In his lecture, Dr. Deljanin proposed a colour grading scale for pink diamonds, ranging from 0 (zero) = light colour, to 10 (ten) = fancy vivid colour. Moreover he showed the characteristics of pink natural, treated and lab-grown diamonds using gem lab instruments. The characteristics examined were the origin (Argyle and other origins including Brazil, Canada, Congo, Russia, Venezuela etc.), the treatments and the lab-growing methods (CVD and HPHT), the visual characteristics, the pattern under polariscope, the LW/SW ultraviolet fluorescence and the spectroscopy on visible and near-infrared (NIR) light.
Dr. Robert Chodelka of Ziemer Swiss Diamond Art AG, Port (Switzerland) related about the two diamond growing processes possessed by his firm, and stressed lab-created diamonds as complimentary to mined diamonds and that growth of diamonds opens the door for new technologie to be found.
The lecture of Dr. Emmanuel Fritsch of the Institute des Materiaux Jean Rouxel and University of Nantes (France) was named “Dissolved Dislocations in Gems: An Overview
”. He stressed dislocations are crystallographic defects which are ideally linear and correspond to a defect induced usually by deformation. An edge dislocation is among the commonest ones. Examples of crystal structure dislocations in several gems were shown. This appearance is sometimes futher modified by filling with a mixture of products. An example is the so-called “rutilated topaz”.
The lecture of Dr. Andy Shen of the Gemmological Institute – China University of Geosciences – Wuhan (China) was named “An Updated Study Of The Role Of H and Fe in Ametrine And Their Relationships With Colour
”. In his speech he showed the X-ray and IR- absorption spectra of natural and synthetic ametrine quartz and demonstrated H and Fe take a very important role for giving those particular colours (yellow and violet) to this interesting variety of quartz. This lecture was the last one of Saturday May 25.
Sunday May 26 started with the lecture of Dr. Federico Pezzotta of the Natural History Museum of Milano (Italy), whose subject was “Madagascar Rubellite: Deposits and Recent Production
”. He mentioned several historical and recently discovered localities producing this gemstone in that big African island, and showed many crystals found in those places.
The lecture of Dr. Tobias Hàger of the Institute of Geosciences - Johannes Gutenberg University – Mainz (Germany) was named “Colombian Emeralds: An Update
”. He showed the chemical composition and deviations and the UV/Vis/NIR absorption spectra of crystals from Muzo and Chivor compared to emeralds of other origins.
Dr. Daniel Nyfeler of the Gùbelin Gem Lab – Luzern (Switzerland) gave his lecture named “Provenance Proof: Technologies For Tracing and Tracking Gemstones Along The Entire Value Chain
”. He related about the methods used by his lab in order to give at least an opinion about the origin of a gemstone; this information is widely requested by consumers.
The lecture of Dr. Claudio Milisenda of the DSEF – German Gem Lab – Idar-Oberstein was named “Spectroscopical Research on Gemstone Structure, Colour and Modification: A DGemG – DSEF Perspective
”. After giving a short history of the use of spectroscopy in gemstone analysis, he related about gemstone enhancement and synthetic gemstones and their detection, and showed several absorption spectra in various gemstones. The most interesting ones were the spectrum of a cuprian elbaite before and after heat treatment at 550°C and the comparison of spectra in two well-known varieties of grossular garnet: tsavolite and hessonite.
The lecture of Dr. Michael Krzemnicki of the Swiss Gemmological Institute SSEF – Basel (Switzerland) was named “Red Ruby Or Pink Sapphire, That's The Question – Where Is The Boundary Between Colour Varieties of Gems?
”. By the way, the German Gemmological Association takes as a rule the sentence “no chrome, no ruby”, and “no chrome, no emerald”, etc. In his lecture, Dr. Krzemnicki showed many borderline cases of ruby/pink sapphire, emerald/green beryl, alexandrite/chrysoberyl, etc., but he also stressed the beauty of gem varieties, no matter what's their name.
The lecture of Dr. Tom Stephan of the DGemG was named “The Role Of V+++ in Gemstones Mainly Coloured By Cr+++, Shown by Spectral Fitting At The Example Of Emerald And Ruby
”. In his lecture he showed the absorption spectra of corundums and beryls coloured by Cr+++ compared to spectra of corresponding stones coloured by V+++ and by both of these elements.
V+++ has a great influence also on colour tone of these gemstones: it produces a more violettish hue in rubies and a less blueish green hue in emeralds, with a weaker pleochroism.
The lecture of Dr. Kenneth Scarratt of the Bahrain Institute for Pearls and Gemstones (Danat) – Manama (Bahrain) was named “A Recent Expedition To Acquire And Characterize Natural Pearls From Australian Pinctada Maxima
”. In his lecture he showed the microscopical characteristics, the X-ray micro-radiography, the X-ray computed microtomography, various forms of spectroscopy and chemical analyses. He also related about the conservation laws and rules which are very strict in Australia; acquiring natural pearls from that country has become therefore very difficult.
The last lecture of the symposium was given by Dr. Ahmadan Abduriyim of the Tokyo Gem Science LLC – Saitama (Japan) and its subject was “The Gemmological Characteristics Of Japanese Freshwater Cultured Pearls From The Lake Kasumigaura
”. In his speech he showed slides of those pearls and absorption spectra of Kasumigaura pearls whose colours ranged from whitish to yellowish, pink, orange, purplish and golden with orient; he also showed some chemical analyses giving evidence of the role of gadolinium and barium in those pearls, but he also related about the seriously bad situation of Japanese lakes (Biwa, Kasumigaura itself, etc.), due mainly to industrial pollution, which makes pearl culturing more and more difficult.