GSA 2016 Annual Meeting
The Geological Society of America (GSA) held its annual meeting September 25–28 in Denver, Colorado. This was the fourth meeting in which GIA hosted gemological technical sessions. In the oral and poster sessions, gemologists, geoscientists, and students from all over the world came together to present their research and discuss advanced topics.
Invited speaker Jeffrey Post (Smithsonian Institution, Washington DC) presented the results from detailed and sustained studies on a selection of significant fancy-color diamonds, including blue, pink and chameleon stones. Among these, the researchers applied time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis to the Hope diamond, which allowed the measurement of total boron concentration; the results revealed strong zoning from this chromophore in many blue diamonds. Graham Pearson (University of Alberta, Canada) reported on his study of the saline fluid inclusions preserved in some diamonds from the Ekati and Diavik mines and pointed out that alkali- and Cl-rich fluids play a key role in diamond formation. Invited speaker Emmanuel Fritsch (University of Nantes, France) discussed the state of synthetic diamond identification. He also noted the advantages and limitations of some of the most commonly used sorting methods.
GIA researchers shared their results on several diamond-related projects. Christopher M. Breeding showed the fluorescence colors and patterns diamonds can display when exposed to ultraviolet light. In addition to their beauty, these colors and patterns are important in diamond formation studies and the identification of natural, treated, and synthetic material. Karen Smit presented new data on a suite of canary diamonds from Sierra Leone. This will allow researchers to further specify the source fluids and color-forming defects of these yellow diamonds and better correlate their features to the unusual geological formation history of the Zimmi diamond deposit. Evan Smith reported his findings on inclusions in thousands of high-quality type II polished diamonds and trimmed-off portions. The recurring set of inclusions in many stones includes a metallic multi-phase assemblage and retrogressed former perovskite phases. Together, the two inclusion types revealed a unique paragenesis for these large, top-quality diamonds.
Presentations on colored gemstone research revealed a variety of studies on important gem species and collector stones. Mandy Krebs (University of Alberta) reported on Pb-Pb geochronology of rubies and the first-ever radiometric age determination of ruby. This new method allows dating to be done directly on the ruby itself rather than on inclusions such as zircon. This dramatically broadens the application of geochronology in ruby provenance determination. Jullieta Lum (University of Johannesburg) presented major and trace element composition of emerald and aquamarine collected from central Namibia and South Africa. Peter Heaney (Penn State University) revealed the cause of iridescence in metamorphic hematite from Minas Gerais, Brazil. The study by Dr. Heaney and his former student Xiayang Lin found that this phenomenon is caused by a framework of well-oriented hematite nanorods. Raquel Alonso-Perez (Harvard University) presented preliminary results on the geochemistry of emeralds from the Irondro deposit in Madagascar.
Important research on gemstone formation was also delivered. Yury Klyukin (Virginia Tech) addressed the valuable information fluid and melt inclusion studies can provide in solving gem formation problems, using diamond, emerald, and corundum as examples. Invited speaker David London (University of Oklahoma) discussed the different mechanisms that caused zonation within pegmatites. Understanding of mineral segregation within pegmatites is critical for gem exploration.
The poster session presenters included two graduate students from the China University of Geosciences (Wuhan). Chengsi Wang proved the robustness of photoluminescence (PL) spectroscopy in treated and synthetic spinel identification through a series of heating and annealing experiments. Yuan Zheng applied linear discriminant analysis (LDA) in separating hundreds of turquoise samples from three different sources after analyzing their trace elements using ICP-MS.
GIA diamond researchers and library staff also presented interesting discoveries in the poster session. Wuyi Wang studied the distribution of the [Si-V]– defect and found that it has a dramatically different correlation with Nii+ between natural and HPHT synthetic diamonds. Paul Johnson demonstrated that hydrogen-rich diamonds with intensive inclusions and fractures can be heated to generate a more uniform black color. Based on his experience, microscopic observation remains the most powerful tool in identifying this treatment. Troy Ardon and Sally Eaton-Magaña conducted a series of annealing experiments at different temperatures with two hydrogen-rich Zimbabwe diamond plates. They evaluated the effect of high temperature on the diamonds’ spectroscopic features and inclusions. Rose Tozer examined one of the rarest publications in the GIA library collection: Russia’s Treasure of Diamonds and Precious Stones. Edited by the well-known mineralogist A.E. Fersman, this book documents Russia’s regalia and crown jewels at the time of the February Revolution in 1917. The volume has been digitized as part of GIA’s project to digitize items from its rare book collection and can be accessed free of charge at https://archive.org/details/gialibrary.
Abstracts from the two gemological sessions can be found at https://gsa.confex.com/gsa /2016AM/webprogram/Session40327.html (oral) and https://gsa.confex.com/gsa/2016AM /webprogram/Session41331.html (poster). The 2017 meeting will be held October 22–25 in Seattle.
