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Gems & Gemology Turns 90!

Duncan Pay, May 3, 2024

An overview of the Spring 2024 Gems & Gemology content.

Texas Topaz, Slovak Opal, a Beryl Inclusions Chart, and More

Duncan Pay, January 26, 2024

An overview of the Winter 2023 Gems & Gemology content.

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Winter 2023 G&G Available Now

Erica Zaidman, January 26, 2024

An overview of the Winter 2023 Gems & Gemology content.

Figure 12. Rough and cut iolite from Blue Bear. From left to right, the faceted stones weigh 1.24, 0.48, 0.48, and 0.88 ct. Photo by Philippe Belley.

Iolite from the Thor-Odin Dome, British Columbia, Canada: Geology, Chemical Composition, Inclusions, and Cause of Chatoyancy

Philippe M. Belley, November 3, 2023

Reports on the geological setting and gemological properties of violet-blue gem cordierite from new deposits located in British Columbia.

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Fall 2025 G&G Available Now

GIA Staff, November 17, 2025

An overview of the Fall 2025 Gems & Gemology content.

Diamonds with the 480 nm Absorption Band, the Morphology of Macle Diamonds, and Russian White Nephrite’s Distinctive “Orange Peel” Texture

Duncan Pay, November 17, 2025

An overview of the Fall 2025 Gems & Gemology content.

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Spring 2024 G&G Available Now

Erica Zaidman, May 3, 2024

An overview of the Spring 2024 Gems & Gemology content.

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Spring 2023 G&G Available Now

Erica Zaidman, May 23, 2023

An overview of the Spring 2023 Gems & Gemology content.

Figure 1. Top production from Rock Creek from the 2021 mining season, in rough and cut form. The rough stones range from 10.05 to 67.15 ct and the faceted stones from 3.09 to 12.18 ct. The yellow sapphire at top center was named the Yellowstone sapphire and is part of the Somewhere in the Rainbow collection. For the faceted stones, the blue stone on the left and the two blue stones on the bottom are heated, while the others are unheated. Note that one of the rough stones is missing in the faceted stone layout. Photos by Robert Weldon; courtesy of Potentate Mining, LLC.

Gemological Characterization of Montana Sapphire from the Secondary Deposits at Rock Creek, Missouri River, and Dry Cottonwood Creek

Aaron C. Palke, Nathan D. Renfro, Jeffrey R. Hapeman, and Richard B. Berg, May 23, 2023

Examines the mining history and geological characteristics of the three secondary sapphire deposits in the state of Montana, as well as the properties of these sapphires (unheated and heat-treated).

Figure 11. Double-strand natural saltwater pearl necklace. Photo by Robert Weldon; courtesy of Karmshil Enterprise. Alexandrite exposed to incandescent illumination (left, red) and daylight-equivalent illumination (right, green). Photos by Robert Weldon; courtesy of GIA’s Dr. Edward J. Gübelin collection, no. 33805. Ring containing a CVD-grown diamond. Photo by Johnny Leung.

Classification of Gem Materials Using Machine Learning

Matthew F. Hardman, Artitaya Homkrajae, Sally Eaton-Magaña, Christoper M. Breeding, Aaron C. Palke, and Ziyin Sun, November 1, 2024

Explores the application of several machine learning models to complement traditional gem classification approaches.

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