Gem News International Gems & Gemology, Fall 2016, Vol. 52, No. 3

Gem Materials at the Second European Mineralogical Conference (emc2016)

The European Mineralogical Conference, organized by the Italian Society of Mineralogy and Petrology (SIMP) and the Universities of Ferrara and Padova, was held in Rimini, Italy, September 11–15. Among the event’s 28 sessions was “Gem Materials,” chaired by this contributor, Lee Groat (University of British Columbia, Vancouver, Canada), Federico Pezzotta (Museum of Natural History, Milan), and David Turner (University of British Columbia). “Gem Materials” yielded both an oral and a poster session.
The poster session, held September 13, covered topics such as worldwide emerald sources; red beryl; demantoid from Madagascar; turquoise from the collections of the Royal Mineralogical Museum of Naples; epidote from Val Malenco, Italy; and rhodonite from the Swiss Alps. There was also a review of colored gems in art and gemology, as well as experimental work applied to gems from miarolitic pegmatites.
The September 15 oral session featured 14 presentations. Dan Marshall (Simon Fraser University, Burnaby, Canada) opened with a keynote address on a reclassification of emerald deposit formation models based on tectonic and metamorphic conditions. Emmanuel Fritsch (Institut des Matériaux, Jean Rouxel, University of Nantes, France) posed the question of why some minerals are gem quality, using crystal growth as a consideration.
Peter Bačik (Comenius University, Bratislava, Slovakia) began the presentations on Cr- and V-bearing minerals with spectrometric characterizations of ruby, spinel, chrysoberyl, diopside, garnet, zoisite, emerald, and tourmaline. Isabella Pignatelli (French National Center of Research, Vandœuvre) studied the Cr- and V-bearing euclase from the Gachala mining district of Colombia, focusing on atypical texture formed by solid inclusions trapped along crystallographic axes. Her presentation opened a discussion of trapiche vs. trapiche-like textures. Dan Marshall spoke again, this time on fluid inclusions and stable isotope data from emerald in Western Australia’s Poona deposit, showing multiple generations of emerald combined with metamorphic and magmatic fluid circulations. This contributor demonstrated that it was possible to decipher the geographic origin of pink and red spinel through oxygen isotopes and trace-element data on pink and red spinels in marble, with a special focus on the Kul-i-Lal mine in Tajikistan. Stefanos Karampelas (GemResearch Swisslab, Adligenswil, Switzerland) offered new insights on detection of heat treatment of tanzanite, indicating that this form of treatment can only be identified under very specific circumstances.
Aaron C. Palke (University of Queensland and Queens­land Museum, Brisbane, Australia) presented on melt inclusions in sapphires from Montana’s Yogo deposit, which are similar in composition and mineralogy to the ocelli observed in the Yogo lamprophyres. David Turner offered new mineralogical insights from near-field hyperspectral imaging of sapphire-bearing marble at Baffin Island, Canada.
The silica family was covered in three presentations. Benjamin Rondeau (University of Nantes) related the presence of numerous minerals (including an unknown type) from the lazulite-bearing blue quartzite from Itremo, Madagascar. Ilaria Adamo (Italian Gemological Institute, Milan) characterized blue and white banded chalcedony (agate) from Yozgat Province in Turkey. The agate formed from mixture of quartz and moganite, but the origin of the blue color is unknown, since iron content at approximately 10 ppm is constant in all the banding. Boris Chauviré (University of Nantes) explained a model for the formation of precious opal from Wegel Tena, Ethiopia. The model suggests a paleotopographic control on the location of the deposits and the repetition of the soil formation process in space and time.
Special topics related to gem museums and historical writings were also covered. William B. “Skip” Simmons (Maine Mineral and Gem Museum, Bethel) retraced the state’s recent and historical gem production and the museum’s acquisitions from Maine pegmatites. Ann C. Pizzorusso (Naples, Italy) tackled the gems of Dante’s Divine Comedy, discussing the gemological knowledge of the late Middle Ages and the meanings associated with precious metals, pearls, rubies, diamonds, and other gems.
Details from the European Mineralogical Conference are available at next conference will take place in 2020 at a site to be determined.

Gaston Giuliani is director of research at the Institute of Research for Development (IRD) in Toulouse (GET) and the French National Center of Research (CRPG/CNRS) in Vandœuvre.