Winter 2020 G&G Available Now
April 5, 2021
The Winter issue covers an array of insightful topics, including treatment detection, geographic origin separation, and more. We open with a characterization study of Madagascan pink sapphire before and after low-temperature heat treatment and the techniques used to detect such treatment. Two articles investigate various advanced analytical methods used for origin determination of blue amber and Vietnamese sapphire, respectively. And faceting patterns of from a bygone era see renewed interest with a historical examination of rose-cut colored stones.
Low-Temperature Heat Treatment of Pink Sapphires from Ilakaka, Madagascar
The lead article, by Sudarat Saeseaw and co-authors, studies the effects of low-temperature heat treatment on inclusions, particularly zircon and monazite crystals, in pink sapphire from this locality. Results show that Raman and Fourier-transform infrared spectroscopy are useful techniques to detect low-temperature heat treatment and may help laboratories set criteria for detecting treatment of this nature.
Baroque-Era Rose Cuts of Colored Stones: Highlights from the Second Half of the Seventeenth Century
Karl Schmetzer provides an in-depth profile on the faceting patterns of colored stones from the Baroque era. In this study, five gem-encrusted objects originally belonging to the archbishops and prince-electors of Trier and Cologne are systematically evaluated to shed light on the variety of rose-cut facet arrangements available during the latter half of the seventeenth century.
Fluorescence Characteristics of Blue Amber from the Dominican Republic, Mexico, and Myanmar
Amber showing very strong blue fluorescence under sunlight is highly sought after in the Chinese gem market. A research team led by Zhiqing Zhang shows that a combination of visual features, UV-Vis-NIR spectroscopy, and excitation-emission mapping can aid in identifying “blue amber” from each of the three principal localities.
Mineral Inclusions in Sapphire from Basaltic Terranes in Southern Vietnam: Indicator of Formation Model
Southern Vietnam plays host to four main sapphire-producing areas, including Dak Nong, Di Linh, Binh Thuan, and Krong Nang. Utilizing advanced analytical techniques, Doan Thi Anh Vu and co-authors study the chemistry of mineral inclusions to reconstruct the formation model of sapphire in this volcanic area. The results of this work are useful for origin determination.
GIA laboratory staff members present their latest findings in the Lab Notes section, including an “all-American” diamond from Crater of Diamonds State Park in Arkansas, a striking purplish pink unheated Montana sapphire, and the largest CVD laboratory-grown diamond submitted to GIA yet.
The Micro-World section, dedicated to the inner world of gemstones, features a pyrope-spessartine garnet proudly displaying an unusual inclusion of blue apatite, a Mogok ruby paired with a rare bright blue lazurite inclusion, and a Mong Hsu ruby containing a partially healed fissure with a snowflake-like pattern of flux residue.
Diamonds from the Deep
Karen Smit and Steven Shirey examine the large-scale tectonic processes that have produced a critical carbon reservoir where the majority of diamonds are stored. Age-dated diamonds from the lithospheric mantle help us better understand continent evolution and carbon cycling between Earth’s crust and mantle.
Gem News International
Finally, GNI correspondents from around the world report on a new emerald locality in Southern California, distinctive dendritic inclusions in Chinese nephrite from Dahua, laser-engraved rock crystal as a new imitation of phantom quartz, and chemical analysis of rhodium-plated etched iron meteorites.
Brooke Goedert is associate editor of Gems & Gemology at GIA in Carlsbad, California.