2014 Sinkankas Symposium on Peridot and Green Gems

Lisbet Thoresen at the 2014 Sinkankas Symposium
At the 2014 Sinkankas Symposium, Lisbet Thoresen presented lectures on peridot from Zabargad and the historical origins of “chrome” chalcedony. Photo by Robert Weldon/GIA.
More than 150 gem enthusiasts attended the twelfth annual Sinkankas Symposium on April 5 at GIA headquarters in Carlsbad, California. The theme for the day was peridot and uncommon green gem minerals.
Cohosted by the Gemological Society of San Diego and GIA, the symposium is held in honor of the famed gem and mineral author John Sinkankas (1915–2002). This year’s event featured 11 half-hour lectures covering a wide range of topics. Symposium organizer Roger Merk, a friend of Sinkankas’s, created a program that blended research, curatorial, and trade perspectives.
Attendees got an in-depth look at important geographic sources of peridot, past and present. Independent gem scholar Lisbet Thoresen, delivering the keynote address on behalf of Dr. James Harrell, described a 2010 archaeological expedition to the ancient mines on the Red Sea island of Zabargad. Dr. Raquel Alonso-Perez, curator of the Harvard Mineralogical and Geological Museum, characterized the geochemical setting of peridot from Pakistan’s Sapat Valley. Dr. George Harlow of New York City’s American Museum of Natural History, showed how the deposits of Mogok, Myanmar, are geochemically similar to those of Zabargad and Sapat Valley.

Raquel Alonso-Perez at the 2014 Sinkankas Symposium Dr. Raquel Alonso-Perez discussed the peridot deposits of Pakistan’s Sapat Valley. Photo by Robert Weldon/GIA.
Also in the technical realm, Dr. William “Skip” Simmons of the University of New Orleans detailed the mineralogical and crystallographic properties of the olivine group. Complementing this talk was a presentation on olivine geology by GIA’s Dr. James Shigley.

William Skip Simmons at the 2014 Sinkankas Symposium Dr. William “Skip” Simmons delivered a talk on the physical properties, chemical composition, and crystal structure of olivine. Photo by Robert Weldon/GIA.
In the afternoon sessions, Nathan Renfro of GIA’s Carlsbad laboratory demonstrated lapidary techniques for improving the optical performance of peridot and compared inclusions from various localities. Ms. Thoresen presented the historical context of the quartz variety known as “chrome” chalcedony. Robert Weldon of GIA overviewed the jewels of the Cheapside Hoard, an archeological trove buried in London centuries ago that included peridot from Zabargad. Dr. Shigley surveyed some lesser-known green gem minerals occasionally used in jewelry. Bill Larson, president of Pala International, presented a gallery of green gem and mineral specimens from his personal collection, several of which were also on display. In the closing address, Dr. George Rossman examined the causes of color in various green gem minerals.
To view symposium abstracts and speaker bios, or to order a copy of the proceedings volume, visit www.sinkankassymposium.net.
According to Merk, opal will be the theme for the 2015 Sinkankas Symposium. The lineup of scheduled speakers includes Dr. Eloïse Gaillou, associate curator of the Natural History Museum of Los Angeles County, and Renée Newman, a leading author of gem and jewelry consumer guides.

Stuart Overlin is the editor of Gems & Gemology in Carlsbad, California.