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Summer 2023 G&G Available Now

Erica Zaidman, August 4, 2023

An overview of the Summer 2023 Gems & Gemology content.

Round brilliant diamond and a photomicrograph of its largest corundum inclusion.

Corundum Inclusions in Gem Diamond

Garrett McElhenny, Michael Turner, and Christopher M. Breeding, July 22, 2020

Rare chromium-rich corundum inclusions in a natural gem diamond provide a window into the deep earth.

Figure 2. Layers of limestone and chert plastically deformed and folded at high pressure and temperature during metamorphism. Photo by Dieter Mueller (dino1948)/licensed under CC BY SA 4.0.

Gems Formed in Metamorphic Rocks

Aaron C. Palke and James E. Shigley, August 4, 2023

Gemstones formed in metamorphic environments offer insights into the earth’s history and the evolution of tectonic activity that led to their formation.

Natural Pipi Pearls from Tahiti

Olivier Segura, Emmanuel Fritsch, and Djamel Touati, April 30, 2014

An overview of natural "pipi" pearls from French Polynesia.

Vietnamese peridot nodules, rough stones, and faceted samples

Peridot from the Central Highlands of Vietnam: Properties, Origin, and Formation

Nguyen Thi Minh Thuyet, Christoph Hauzenberger, Nguyen Ngoc Khoi, Cong Thi Diep, Chu Van Lam, Nguyen Thi Minh, Nguyen Hoang, and Tobias Häger, November 7, 2016

Analyzes the gemological and geochemical characteristics of peridot from the Gia Lai province alongside specimens from other localities to gain insight into its formation.

Faceted peridot from the Pyaung-Gaung mine in Mogok

Gemological Characterization of Peridot from Pyaung-Gaung in Mogok, Myanmar

Montira Seneewong-Na-Ayutthaya, Wassana Chongraktrakul, and Tasnara Sripoonjan, January 28, 2022

Examines the mining and the internal, spectroscopic, and chemical features of peridot from this deposit, which possesses a rich olive green color and is available in large sizes.

Figure 1. A 4.56 ct rough diamond with plastic deformation lines, highlighted in the sketch on the right. Deformation has occurred along a set of parallel internal slip planes. The planes appear as thin ridges on the diamond’s surface, exposed by natural dissolution of the surface by fluids (i.e., resorption). In fact, the whole surface has been resorbed into this overall dodecahedroid shape, decorated by elongate hillocks and plastic deformation lines, both fine features representing slight interruptions and imperfections in the diamond crystal lattice. Images by Evan M. Smith.

Plastic Deformation: How and Why Are Most Diamonds Slightly Distorted?

Evan M. Smith, May 23, 2023

A look at plastic deformation, one of the most prevalent features in natural diamond.

Figure 1. These examples of gem minerals that formed in magmatic environments are part of GIA’s Eduard Gübelin Collection. From top to bottom and left to right: 29.96 ct sanidine feldspar from Germany, 53.00 ct peridot from Myanmar, 11.58 ct zircon from Thailand, 20.66 ct topaz from Utah, 2.05 ct sapphire from Thailand, 18.36 ct pyrope garnet from the Czech Republic, 19.55 ct black spinel from Thailand, and 2.50 ct ruby from Thailand. Photos by Robert Weldon.

Gems Formed in Magmatic Rocks

Aaron C. Palke and James E. Shigley, January 25, 2023

This installment of “Colored Stones Unearthed” covers gemstones that formed in magmatic environments and the insights they offer into the evolution of the earth and the geological processes that shaped our world.

Research on Gem Feldspar from the Shigatse Region of Tibet

Ahmadjan Abduriyim, Shane F. McClure, George R. Rossman, Thanong Leelawatanasuk, Richard W. Hughes, Brendan M. Laurs, Ren Lu, Flavie Isatelle, Kenneth Scarratt, Emily V. Dubinsky, Troy R. Douthit, and John L. Emmett, July 25, 2011

The existence of a natural red andesine deposit in China/Tibet has been the subject of controversy since 2006.

Sapphire crystal from Kataragama, Sri Lanka

Geology of Corundum and Emerald Gem Deposits: A Review

Gaston Giuliani and Lee A. Groat, January 31, 2020

Over the last two decades, knowledge of the formation of gem deposits has improved significantly. This article reviews the state of our knowledge of the geology and genesis of gem corundum and emerald deposits.

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