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Hand holding demantoid garnet rough in matrix.

Article

The Latest in Field Gemology from Wim Vertriest: Sapphires and Demantoid Garnets from Northern Madagascar

Phoebe Shang and Wim Vertriest, March 22, 2024

Learn the latest on Madagascar sapphires and demantoid garnets from Wim Vertriest, GIA Manager of Field Gemology.

Article

Winter 2023 G&G Available Now

Erica Zaidman, January 26, 2024

An overview of the Winter 2023 Gems & Gemology content.

Figure 1. A silver brooch containing a large Slovak opal (77 ct, 34.5 × 25 × 13 mm) and 48 diamonds. The opal was initially purchased for Louis XVIII’s personal collection. In 1824, it adorned the clasp of Charles X’s coronation mantle, and around 1853 it was remounted onto this brooch for Empress Eugénie, which has been preserved. Photo by Peter Semrád; courtesy of the National Museum of Natural History in Paris (inventory no. MNHN 87.44).

Slovak Opal: A New Life for a Historical Gem

Peter Semrád, January 26, 2024

Reports on the recent production of precious and common opal from a centuries-old locality.

Figure 1. Sedimentary rocks are among the most common rocks exposed on the earth’s surface. This image shows multicolored sandstone layers known as “The Wave” that have been eroded and sculpted by winds to form a swirling pattern of rock strata in the Coyotes Buttes North wilderness area along a portion of the Arizona/Utah border. Photo by Greg Bulla.

Gems Recovered from Sedimentary Rocks

James E. Shigley, Roy Bassoo, and Aaron C. Palke, January 26, 2024

Explores the formation of sedimentary rocks, gems found and formed in sedimentary environments, and the alluvial mining of these gems.

Figure 1. Artisanal mining in Liberia. Courtesy of Diamonds for Peace.

Artisanal Diamond Mining: Addressing the Knowledge Gap

Beth West, January 26, 2024

Diamonds for Peace conducts basic training on rough diamond grading for artisanal miners in Liberia.

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

Duncan Pay, January 26, 2024

An overview of the Winter 2023 Gems & Gemology content.

Figure 1. Gem materials from southeast Vietnam. The three largest yellow and white samples on the far left are feldspar, while the brown, orange, and near-colorless samples in the center are zircon and the two greenish white samples near the top right are hyalite opal. The rest of the dark stones are sapphires, garnets, augites, and brown peridot. Photo by Le Ngoc Nang; courtesy of Tran Ngoc Vien.

Mining Basalt-Related Gems in Southeast Vietnam

Le Ngoc Nang, Pham Minh Tien, and Ho Nguyen Tri Man, November 3, 2023

Gems from seven gemstone occurrences identified within the basaltic fields in southeast Vietnam are analyzed.

Large sunstone rough from the Ponderosa mine in Oregon

Ponderosa Sunstone Update

Duncan Pay, May 11, 2018

John Woodmark provides an update on the Ponderosa sunstone mine in Oregon.

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.

A 7.94 ct rectangular step-cut rhodochrosite from the Sweet Home mine in Colorado’s Alma Mining District. Photo by Robert Weldon; courtesy of Barker & Co.

Sweet Home Mine Rhodochrosite from 1888

Erin Hogarth, May 23, 2023

A rhodochrosite on display at AGTA dates back more than a century to Colorado’s Alma Mining District.

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