Dive Into Summer: Mozambique Ruby, Madagascar Sapphire, and Black Nephrite from China, Plus an Opal Inclusions Chart
With 2019 already past the halfway mark, we are very pleased to present our Summer edition. Inside you’ll find new insights into a variety of gem materials.
The issue leads with a review of the past decade of ruby from Mozambique. Since 2009, Mozambique has become the world’s leading supplier of ruby, transforming the market in the process. GIA has been visiting these deposits since the initial discoveries, and now Wim Vertriest and Sudarat Saeseaw from the Bangkok laboratory add a new chapter to this story with an overview of production and distribution, as well as a comprehensive gemological characterization and a discussion of the most common treatment processes applied to material from this important locality.
Next, Billie Hughes from Lotus Gemology and Rosey Perkins with Fura Gems present the results of low-temperature heat treatment experiments on sapphire from Madagascar. Increasing numbers of these stones are being heated to relatively low temperatures (below 1350°C) to lighten their color. The authors show the changes in these goods, providing a means of separating unheated and heated Madagascar sapphire.
Moving from Africa to Asia, the issue continues with a study of black nephrite from a deposit in southern China. Qian Zhong, a PhD student of mineralogy at Tongji University in Shanghai, leads a team of professors from that university in characterizing 12 nephrite samples from the Guangxi region.
In the fourth article, Jean-Pierre Gauthier from the Gemological Research Center of Nantes and his coauthors characterize “flame structure” in 37 pearls from bivalves of the Tridacnidae family. Careful observation revealed evidence of rotation during growth, a feature also seen in numerous pearls from Pinctada margaritifera.
The next article, also on pearls, presents an unusual identification challenge that confronted researchers at the Max Planck Institute for Chemistry, Johannes Gutenberg University, and GIA’s New York and Bangkok laboratories. Two pearls were examined by the team of authors, who were unable to positively identify their origin (natural or cultured), their growth environment (freshwater versus saltwater), or the mollusk that produced the pearls.
In our last article, Nathan Renfro and coauthors present an opal inclusions chart, the fifth in their series on micro-features in gemstones. Laminated versions of all of these large, colorful wall charts are also available at store.gia.edu.
Highlights from the Lab Notes column include a rough diamond with a coating of fake green “radiation stains,” a study on the separation of kornerupine and prismatine, and the first report of a color-change spessartine garnet examined by GIA. Gem News International features brief but thorough studies on the gemological characteristics of jadeite from the Polar Urals of Russia, more than 800 natural freshwater pearls from the Mississippi River system, and rubies from the Rock Creek deposit in Montana. As always, Micro-World reveals a fascinating gallery of inclusion scenes, while the Diamonds from the Deep section (now a year old) outlines the basic geological and practical features of kimberlites, the earth’s diamond delivery system.
We hope you enjoy the Summer 2019 edition of Gems & Gemology!