Spring 2021 G&G Available Now


A variety of topics are in store for you in the Spring issue of G&G. First up is a study of the internal structures of natural pearls collected from wild marine mollusks. The second article explores the effectiveness of resin as a pore-filling treatment to improve the appearance of rough turquoise specimens. Next, visible spectroscopy and a mathematical function are used to predict the color of a uniaxial gem material when viewed in any direction. And spinel, which has become increasingly popular among jewelry artisans and aficionados, inspires a colorful chart displaying the many types of inclusions found in this fascinating gem.

Internal Structures of Known Pinctada maxima Pearls: Natural Pearls from Wild Mollusks

This issue’s lead article, by Artitaya Homkrajae and fellow pearl researchers from GIA, spotlights the importance of reliably sourced natural pearl samples. With the help of the Paspaley Pearling Company, the GIA team collected wild P. maxima mollusks off the coast of Australia to compare their internal structures with those of pearls from other sources. This study adds to gemologists’ understanding of natural pearl identification.

Technical Evolution and Identification of Resin-Filled Turquoise

China’s Hubei Province has long been a source of commercial turquoise production. Using a variety of detection techniques, Ling Liu and a team from the Gemmological Institute, China University of Geosciences in Wuhan researched the widespread treatment of filling porous turquoise with resin. Their conclusion was that this is an effective method of improving rough turquoise quality and, like any treatment, should be disclosed to consumers.

How to Calculate Color from Spectra of Uniaxial Gemstones

Understanding the color characteristics of a gemstone can provide a scientific basis to guide its cutting. This study uses visible spectroscopy and a mathematical method to determine the unpolarized spectra of a uniaxial material from the polarized spectra (o-ray and e-ray) in order to predict the color of a uniaxial gem material when viewed in any direction.

Micro-Features of Spinel

Nathan Renfro and co-authors add to the G&G series of micro-feature charts with this lovely display of inclusions found in spinel, a previously under-appreciated gem that is now gaining in popularity due in part to its wide range of colors. The chart is included in every printed copy of this issue, and a laminated version is available for sale in the GIA Store.

Lab Notes

GIA laboratory staff present their latest findings in the Lab Notes section, including two diamond cabochons displaying rare asterism, a precious cat’s-eye opal with patches of color producing distinct chatoyancy, and a lead glass-filled laboratory-grown ruby.

Micro-World

The Micro-World section, which highlights the inner world of gemstones, includes a remarkable cloudlike inclusion resembling a faceted brilliant diamond situated inside a polished diamond, a Mexican opal featuring a rare fluid inclusion with a mobile gas bubble, and a blue sapphire whose strikingly iridescent “play-of-color” along large partially healed fissures demonstrate thin-film interference typical of heat-treated corundum.

Gem News International

GNI correspondents from around the world offer a virtual report on the state of the gem and jewelry trade more than a year into the COVID-19 global pandemic. Other highlights include a geode with a striking resemblance to the Cookie Monster character, a historical hand-drilled briolette diamond, and a stunning photo gallery from the collection of the Alfie Norville Gem and Mineral Museum in Tucson, which reopens in 2021.

The Spring issue also contains the 2021 Gems & Gemology Challenge. Score 75% or better and you’ll receive a certificate of completion (PDF file); earn a perfect score and your name will be listed in the Fall 2021 issue. Online entries for the Challenge must be submitted by Monday, August 2, 2021.

Brooke Goedert is associate editor of Gems & Gemology at GIA in Carlsbad, California.