Summer 2023 G&G Available Now

Erica Zaidman

August 4, 2023

The summer issue of G&G is packed with interesting new content! In our three feature articles, read about a newly discovered treatment in spinel, a find of augite in Vietnam, and the origin of mammoth ivory’s brown color. In addition to these articles and our regular quarterly sections, we see the return of Colored Stones Unearthed and finish the issue with a spotlight on fire obsidian.

COLOR MODIFICATION OF SPINEL BY NICKEL DIFFUSION: A NEW TREATMENT

Dr. Michael Jollands and GIA researchers share their study of a new color treatment for natural spinel, which turns lightly colored stones into deeper blue and green hues. Their analysis of a set of faceted spinel submitted as “cobalt diffused” revealed that the gems were actually diffused with nickel. With this treatment likely to become more common in the gem market, the team also suggests criteria for identifying nickel diffusion in blue and green spinel.

GEM-QUALITY AUGITE FROM DONG NAI, VIETNAM

A team led by Le Ngoc Nang reports on a variety of gem-quality augite from Dong Nai, Vietnam. Characterized by intense dark brown or dark green colors when viewed in transmitted light, the augite is classified as magnesium-rich and has potential for use in jewelry and in carvings.

ORIGINS OF COLOR IN BROWN MAMMOTH IVORY

Mammoth ivory is most commonly found with a brown surface color. Zhaoying Huang and coauthors investigate the origin of this brown color by studying mammoth ivory samples’ spectroscopic and mineralogical characteristics, surface morphology, and chemical composition. They determine that formation of iron oxides, manganese oxides, manganese hydroxides, and iron sulfides on the ivory underground resulted in the brown surface color.

LAB NOTES

GIA’s global laboratory staff present their latest findings in the Lab Notes section, including yellow zoning in unusual natural pink diamonds, invisible markings in CVD laboratory-grown diamonds, and an exceptionally large South Sea cultured pearl.

MICRO-WORLD

The Micro-World section, dedicated to the inner world of gemstones, highlights thread-like serpentine inclusions in brown peridot, a globular iron stain and curved lines in yellow sapphire, an interesting metal sulfide inclusion in garnet, and more.

COLORED STONES UNEARTHED

Colored Stones Unearthed returns to examine gem minerals that form in metamorphic environments, such as jade, corundum, tanzanite, and tsavorite garnet. Studying these gems offers gemologists insight into the evolution of tectonic activity that led to their formation.

GEM NEWS INTERNATIONAL

GNI contributors cover a wide variety of topics, ranging from reports on several pearl species to a new treatment used to create phantom structure in opal. The section also includes a roundup of the spring 2023 auction highlights and recaps of the 2023 Sinkankas Symposium and the sustainability panels at the JCK show in Las Vegas.

IN THE SPOTLIGHT

Lastly, we spotlight fire obsidian, a rare volcanic glass found only in the Glass Buttes region of Oregon. Lapidary artist Tom Dodge shares his work revealing a vibrant spectrum of iridescent colors.