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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).

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.

Gem Rhodochrosite from the Sweet Home Mine, Colorado

Kimberly Knox and Bryan K. Lees, June 1, 1997

New mining techniques have combined state-of-the-art equipment and technology to detect and extract large, fine-quality rhodochrosite specimens and gem rough.

The Effects of Heat Treatment on Zircon Inclusions in Madagascar Sapphires

Wuyi Wang, Kenneth Scarratt, John L. Emmett, Christopher M. Breeding, and Troy R. Douthit, July 25, 2006

Zircon inclusions in sapphires from Madagascar were studied to investigate the effects of heat treatment on their gemological and spectroscopic features.

Gems on Canvas: Pigments Historically Sourced from Gem Materials

Britni LeCroy, November 11, 2022

Explores the use of gem materials as pigments in works of art, from the earliest cave paintings to the modern era.

The Rubies of Burma: A Review of the Mogok Stone Tract

Peter C. Keller, December 1, 1983

A review of the history of this area, its geology, and the mining methods that have predominated.

Article

Fall 2022 G&G Available Now

Brooke Goedert, November 11, 2022

An overview of the Fall 2022 Gems & Gemology content.

Figure 9. The parcel of rough spinel on the left, reportedly from Tajikistan, contains pieces weighing up to 48.5 g. The seven faceted spinels on the right (9.04–28.16 ct) were fashioned from some of this rough.

Purplish Pink Spinel from Tajikistan: Before and After Cutting

Nicholas Sturman, March 1, 2009

Purplish Pink Spinel from Tajikistan: Before and After Cutting

Separating Natural and Synthetic Rubies on the Basis of Trace-Element Chemistry

Sam Mulhmeister, Emmanuel Fritsch, June 1, 1998

Natural and synthetic gem rubies can be separated on the basis of their trace-element chemistry.

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