Dive into the Summer 2019 Gems & Gemology (G&G), GIA's (Gemological Institute of America) quarterly professional journal, for insights into Mozambique ruby, Madagascar sapphire, black nephrite from China, pearls and opal inclusions. The latest G&G is available in print by subscription and in the GIA Store, and digitally – at no cost – on GIA.edu.

GIA field gemologist Wim Vertriest and senior manager of identification Sudarat Saeseaw open the issue with a review of ruby from Mozambique that explores a decade of production, distribution, gemological characterization and the most common treatment processes applied to material from this locality. Billie Hughes of Lotus Gemology and Rosey Perkins with Fura Gems present their findings of low-temperature heat treatment experiments on sapphire from Madagascar and the means for separating unheated from heated stones. Also, lead author and PhD student of mineralogy at Tongji University Qian Zhong shares the study of black nephrite jade from Guangxi, southern China that appears to be part of a large-scale jade formation belt in the region.

Pearls are the focus in two of the articles in the summer issue. 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 that revealed evidence of rotation during growth. Researchers at the Max Planck Institute for Chemistry, Johannes Gutenberg University, and GIA's New York and Bangkok laboratories share a pearl identification challenge, where two pearls could not be positively identified at any of these gemological laboratories.

In the final feature, GIA manager of colored stone identification Nathan Renfro and coauthors present a large and colorful opal inclusions chart that is also available as a laminated wall chart from the GIA Store online. Lab Notes includes a rough diamond with 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.

The issue is rounded out with the regularly occurring features G&G Micro-World, Diamonds from the Deep and Gem News International.

This and every issue of G&G since 1934, including full articles, lab notes, photo galleries and exclusive video footage, is available at no cost on GIA's website GIA.edu/gems-gemology.

Additional research articles are available at GIA.edu/gia-news-research.

Print subscriptions and copies of back issues are available at http://store.gia.edu/.

The platinum pendant shown on the Summer 2019 cover of Gems & Gemology features a 9.39 ct black opal accented by 0.25 ct pear-shaped diamond and 0.90 carats of round Paraíba tourmalines. Designed by Niveet Nagpal, courtesy of Omi Privé. The background is a photomicrograph of a black opal from Lightning Ridge, Australia, showing broad, angular flashes of play-of-color known as a harlequin or mosaic pattern. Diffuse reflected light, vertical field of view approximately 12 mm. Photomicrograph by Nathan Renfro.