Editorial Gems & Gemology, Winter 2020, Vol. 56, No. 4

Pink Sapphires from Madagascar, Rose-Cut Colored Stones from the Baroque Era, Separating Blue Amber Localities, and More…

Duncan Pay

Welcome to the Winter 2020 issue of Gems & Gemology! This issue brings an exciting conclusion to the volume year with a study on low-temperature heat treatment of pink sapphire, a characterization of rose cuts that adorn rare artifacts of a bygone era, and the means to separate the three principal localities for blue amber.

“A characterization of rose cuts that adorn rare artifacts of a bygone era…”

In the lead article, a team led by Sudarat Saeseaw examines the effects of low-temperature heat treatment on inclusions in pink sapphire from Ilakaka, Madagascar. The detailed characterization of these samples before and after heating will help laboratories develop treatment detection criteria. This study also presents a useful technique using Fourier-transform infrared (FTIR) spectroscopy to detect low-temperature heat treatment of this material.

In the second article, researcher Karl Schmetzer returns to the pages of G&G with an evaluation of seventeenth-century colored stones fashioned as rose cuts, which richly decorate rare artifacts once belonging to archbishops and prince-electors of Trier and Cologne. This article seeks to fill a gap in the historical record, as rose-cut colored stones have been mainly overlooked in favor of their diamond counterparts.

Next, Zhiqing Zhang and a team from the Gemmological Institute, China University of Geosciences in Wuhan use observation, UV-Vis-NIR spectroscopy, and excitation-emission mapping to separate blue amber mined from the Dominican Republic, Mexico, and Myanmar. This widely loved organic gemstone may be grouped according to very strong blue fluorescence and distinct emission and excitation wavelengths.

In the final article, Doan Thi Anh Vu from Vietnam National University heads an investigation of mineral inclusions in basaltic sapphire from southern Vietnam. The team analyzes inclusion chemistry using EPMA to understand the formation model of these sapphires in relation to the basaltic volcanism of this locality.

As always, our regular columns feature an array of interesting gemological findings. Highlights of from Lab Notes include a large “all-American” diamond from Arkansas and artificial glass prisms masquerading as Paraíba tourmaline. Micro-World enchants with the inner beauty of gems: lazurite and snowflakes in Burmese ruby from Mogok and Mong Hsu, respectively, and sapphires exhibiting elongated rutile. Stay up to date in the Gem News International section with a new emerald locality in Southern California and the use of rhodium plating on etched iron meteorites. Diamonds from the Deep returns with a unique perspective on how diamond ages can help us understand continent evolution spanning billions of years.

Finally, we include a reprint of the Spring 2020 article by Emily Dubinsky et al. (“A Quantitative Description of the Causes of Color in Corundum”) to correct the color of several photos and areal color density circles. We regret these errors and have used the opportunity to produce a new wall chart displaying the corundum chromophores from this article.

We hope you enjoy our Winter issue!

Duncan Pay is editor-in-chief of Gems & Gemology.