Delve into the science of green diamonds, explore “rainbow” hematite and discover how DNA can be used to identify pearls in the Spring 2018 issue of Gems & Gemology (G&G), GIA’s (Gemological Institute of America’s) quarterly professional journal. The spring issue will also feature the 2018 G&G Challenge, a 25-question multiple-choice quiz based on articles published in 2017– Those who score 100% will be listed in the Fall 2018 issue. The Gem News International section will carry a complete report on the February 2018 Tucson gem and mineral shows, with 24 pages of coverage and photos. G&G’s Spring 2018 issue is available in print by subscription and in the GIA Store, and digitally – at no cost – on GIA.edu.
This issue opens with “Natural-Color Green Diamonds: A Beautiful Conundrum,” the first in a series of articles about fancy-color diamonds. Christopher M. Breeding, Sally Eaton-Magaña and James E. Shigley compiled data representative of more than 9,000 samples to offer a look at natural green diamonds that has never before been possible. These diamonds are colored either by simple structural defects produced by radiation exposure or by more complex defects involving nitrogen, hydrogen or nickel impurities. Laboratory irradiation treatments closely mimic the effects of natural radiation exposure, causing tremendous difficulty in gemological identification – a challenge that the three GIA research scientists address in this article.
“Iridescence in Metamorphic ‘Rainbow’ Hematite” explores “rainbow” hematite from Minas Gerais, Brazil. The authors, Xiayang Lin, Peter J. Heaney and Jeffrey E. Post, use advanced technology to determine the cause of the intense wide-angle iridescence. The study revealed that the interference is produced by a repeating microstructure consisting of spindle-shaped hematite nanocrystals containing minor impurities.
G&G continues with “DNA Techniques Applied to the Identification of Japanese Pinctada Fucata Pearls from Uwajima, Ehime Prefecture, Japan.” Kazuko Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessrapong and Nicholas Sturman share how genetic information encoded in deoxyribonucleic acid (DNA) can be used to identify this akoya cultured pearl species.
Additional highlights include a recent lab note by Sally Eaton-Magaña on five CVD synthetic diamonds larger than three carats and beautiful photomicrographs in the Micro-World section of an opal with agate-like banding.
This and every issue of G&G since 1934, including full articles, lab notes, photo galleries and exclusive video footage, are available at no cost on GIA’s website at https://www.gia.edu/gems-gemology.