Gem News International Gems & Gemology, Summer 2015, Vol. 51, No. 2

2015 Sinkankas Symposium

Mexican opal in rhyolite, from the collection of the Mineralogical and Geological Museum at Harvard University.
This Mexican opal in rhyolite is from the Iris mine, Hacienda Esperanza, in Querétaro. The Mineralogical and Geological Museum at Harvard University, received this specimen as a donation from James Garland in 1892, facilitated by George Frederick Kunz. It measures 7 × 6 cm and is the finest opal in the museum’s collection. Photo by Robert Weldon/GIA, courtesy of the Mineralogical and Geological Museum, Harvard University.

The thirteenth annual Sinkankas Symposium was held April 18 at GIA headquarters in Carlsbad, California. Co-hosted by the Gemological Society of San Diego, GIA, and Pala International, the event drew a capacity crowd eager to learn about opal.

After welcoming remarks from organizer Roger Merk, the morning presentations began with an overview by Dr. Eloïse Gaillou (Paris School of Mines) on geology, color, and microstructure. Andrew Cody (Cody Opal, Melbourne) chronicled the Australian opal market before delving into fossilized specimens. Dr. Raquel Alonso-Perez (Mineralogical and Geological Museum, Harvard University, Cambridge, Massachusetts) spoke on the history of the museum and shared photos and data of specimens from its collection. Photographer Jack Hobart showed superb images from his extensive database of Mexican opals. Bill Larson (Pala International, Fallbrook, California) described his personal collection of Mexican, Australian, Ethiopian, and Brazilian opals, many of which were on display throughout the campus.

The afternoon sessions began with a presentation by Alan Hart (Natural History Museum, London) on the museum’s opal collection. Noted lapidary Meg Berry (Megagem, Fallbrook, California) described various techniques for cutting and carving. Buying guide author Renée Newman (International Jewelry Publications, Los Angeles) discussed the jewelry uses of matrix and common opal. Helen Serras-Herman (Gem Art Center, Rio Rico, Arizona) followed with additional insight on the many varieties of common opal. Robert Weldon (GIA, Carlsbad) discussed the challenges of photographing opal’s shifting flashes of color, as well as the instruments and post-production techniques best suited to the task. Nathan Renfro (GIA, Carlsbad) looked at the gem’s internal features and the wide range of mineral inclusions that create vibrant, colorful scenes. Dr. George Rossman (Caltech, Pasadena, California) examined causes of color and offered closing remarks.

Sapphire will be the theme of the 2016 symposium. For more information on the event or to purchase the proceedings volume, visit

Stuart Overlin is the managing editor of Gems & Gemology.