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Fall 2023 G&G Available Now

Erica Zaidman, November 3, 2023

An overview of the Fall 2023 Gems & Gemology content.

Cause of Color in Yellow Sapphire, Plus Characterization of Oregon Sunstone, Ukrainian Beryl, and British Columbian Iolite

Duncan Pay, November 3, 2023

An overview of the Fall 2023 Gems & Gemology content.

Figure 1. Mantle eclogite xenolith (2.8 cm in longest dimension) consisting of clinopyroxene (green) and garnet (red-orange), with a partially exposed octahedral diamond. Photo by Annie Haynes. Gift of Mark Mauthner, GIA Museum no. 37511.

Diamondiferous Mantle Eclogite: Diamond Surface Features Reveal a Multistage Geologic History

Matthew F. Hardman and Mei Yan Lai, November 3, 2023

Reports on the analysis of a mantle eclogite xenolith with a partially exposed octahedral diamond.

This iridescent ferropericlase crystal with a stress halo measuring approximately 0.7 mm was trapped inside a light brown diamond. Photomicrograph by Kyaw Soe Moe; field of view 1.58 mm.

Iridescent Inclusion in Brown Diamond

Kyaw Soe Moe, November 3, 2023

An iridescent crystal with a stress halo is observed in a light brown diamond.

This etch channel seen in the crown facets of a 1.00 ct diamond with SI<sub>1</sub> clarity (left) resembled a <em>gada</em> (right), a mace-like weapon wielded by the Hindu god Hanuman. Photomicrograph (left) by Deepak Raj; field of view 0.80 mm. Photo (right) courtesy of the Metropolitan Museum of Art.

Inclusion Resembling a Gada in Diamond

Rujal Kapadia, Bhavya Maniar, and Sally Eaton-Magaña, November 3, 2023

An etch channel in the crown facets of a diamond resembles a mace-like weapon.

A well-formed colorless breyite crystal reminiscent of a stone making a splash in water. Photomicrograph by Aprisara Semapongpan; field of view 1.07 mm.

Breyite in Diamond

Aprisara Semapongpan, November 3, 2023

A colorless transparent crystal inclusion in diamond is reminiscent of a stone splashing in water.

Figure 1. Table (left) and pavilion (right) views of a chameleon diamond with visible trigons and tetragons. The trigons and tetragons are shown in more detail in figures 2 and 3. The diamond measures 1.28 cm in length. Photo by Adriana Robinson.

Etch Features Reveal the Morphology of Diamond

Mei Yan Lai and Matthew Hardman, November 3, 2023

Trigons and tetragons observed in a chameleon diamond indicate both octahedral and cubic growth.

Figure 2. Rectangular step-cut green beryl from the Volyn pegmatite, 190.00 ct and 28.55 × 39.02 × 21.71 mm, with a rough unpolished table containing etch pits. Faceting and photo by Konstantyn Zalizko.

Etch Pits in Heliodor and Green Beryl from the Volyn Pegmatites, Northwest Ukraine: A Diagnostic Feature

Gerhard Franz, Oleksii A. Vyshnevskyi, Volodymyr M. Khomenko, Peter Lyckberg, and Ulrich Gernert, November 3, 2023

Examines dissolution features of heliodor and green beryl from a Ukrainian pegmatite field and offers criteria to distinguish them from samples found in other localities.

Figure 1. Mineral inclusions in diamond. This connected pair of green clinopyroxene and orange garnet indicates that diamond growth occurred within an eclogitic mantle host rock. Photomicrograph by Nathan Renfro; field of view 2 mm.

Eclogite: Diamond-Encrusted Ancient Seafloor

Evan M. Smith and Matthew F. Hardman, November 3, 2023

Explores eclogitic diamonds, which make up a significant portion of the gem diamond market, and what they reveal about Earth’s dynamic processes.

This pristine hexagonal platelet of graphite was seen in a pink sapphire from Sri Lanka. Photomicrograph by Jeffrey Hernandez; field of view 1.99 mm.

Pink Sapphire with Graphite Inclusion

Jeffrey Hernandez, August 4, 2023

A hexagonal platelet of graphite is discovered in a pink sapphire from Sri Lanka.

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