Includes detailed explanations of GIA’s origin determination procedures
The Winter 2019 Gems & Gemology (G&G), the latest edition of GIA’s (Gemological Institute of America) quarterly professional journal, is devoted to an important discussion of the science, issues and limitations of geographic origin determination for colored stones by gemological laboratories.
“Origin determination for colored gems is the most challenging aspect of gem identification, and a significant issue for the gem and jewelry trade as well as consumers,” said Thomas M. Moses, GIA executive vice president and chief laboratory officer. “Sharing how GIA determines geographic origin and being transparent about the limits of what science can accomplish are central to our public benefit mission.”
The opening article, “The Geographic Origin Dilemma,” by Shane F. McClure, global director of colored stone services at GIA; Moses; and GIA Distinguished Research Fellow Dr. James E. Shigley, sets out why the professional journal focused on this single topic.
The article states the purpose of the issue: “to lay out what we know about determining geographic origin and how we arrive at those opinions. We intend for this issue to promote healthy and useful discussion and debate – fueled by our collective interest in bringing more understanding and consistency to the reporting of the geographic origin of colored stones.”
The article goes on to point out that a gemstone’s characteristics – from inclusions to trace elements – are determined by geology, not geography. “Where lines have been placed on a map to mark country boundaries is completely irrelevant to where gems form. The geologic conditions needed to form gemstones can occur in many countries and often do not respect geographic boundaries.”
The 230-page journal – the largest G&G issue ever – features articles by GIA staff and other scientists, including GIA Governor Dr. Barbara L. Dutrow, Williams Distinguished Alumni professor of geology and geophysics at Louisiana State University. Collectively, the articles describe the gemological observations and advanced analytical tools and methods applied in GIA’s laboratories to arrive at opinions about geographic origin for ruby, sapphire, emerald, copper-bearing (i.e., “Paraíba”) tourmaline and alexandrite.
Another article describes GIA’s extensive field gemology program, which gathers verified samples from known gem deposits. The reference data gleaned from these carefully cataloged samples, along with skilled and experienced gemologists and advanced scientific instrumentation, are all necessary to form expert opinions on origin.
Because of the singular focus of the issue, regular features – Lab Notes, Micro World, Gem News International and Diamonds from the Deep – will return in the Spring 2020 issue. This and every issue of G & G since 1934, including full contents, photo galleries and exclusive video footage, is available at no cost on GIA’s website GIA.edu/gems-gemology.
News Source: diamondworld