
The quarterly journal of the gemological institute of america

IN THIS ISSUE LABEL
- Natural-Color Blue, Gray, and Violet Diamonds: Allure of the Deep
- Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions
- An Early Byzantine Engraved Almandine from the Garibpet Deposit, Telangana State, India: Evidence for Garnet Trade Along the Ancient Maritime Silk Road
- Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics
- Sapphires from Yogo Gulch, Montana
- Chart: Features of Synthetic Diamonds
EDITORIAL
Summer Reading: Diamond Research, Yogo Sapphire, and Byzantine Garnet
Duncan Pay, Editor-in-Chief
An overview of the Summer 2018 Gems & Gemology content.
Articles (6)

Natural-Color Blue, Gray, and Violet Diamonds: Allure of the Deep
Summarizes data collected on more than 15,000 natural blue/gray/violet diamonds examined by GIA during the last decade and examines the mechanisms that produce this color range.

Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions
Characterizes a suite of 40 natural brown to black diamonds from this deposit so that they can be distinguished from suspected treated black diamonds.
An Early Byzantine Engraved Almandine from the Garibpet Deposit, Telangana State, India: Evidence for Garnet Trade Along the Ancient Maritime Silk Road
Analyzes the chemical composition and inclusion characteristics of this ancient artifact.

Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics
Examines Japanese “Kasumiga” freshwater cultured pearls, which grow in a variety of colors.

Gemological Characterization of Sapphires from Yogo Gulch, Montana
A look at the mining and distinguishing characteristics of this naturally vibrant blue sapphire.

Features of Synthetic Diamonds
Presents a visual guide to the growth processes and major gemological spectroscopic features of synthetic diamonds.
Regular Features



GEM NEWS INTERNATIONAL
Global coverage of gem sources, notable new gem materials, and recent industry developments.
Diamonds From the Deep
Explores the role of diamonds in our understanding of the natural world.

THE DR. EDWARD J. GÜBELIN
MOST VALUABLE ARTICLE AWARD

Big Sky Country Sapphire: Visiting Montana’s Alluvial Deposits
Tao Hsu, Andrew Lucas, Robert E. Kane, Shane F. McClure, and Nathan D. Renfro

Colombian Emerald Industry: Winds of Change
Darwin Fortaleché, Andrew Lucas, Jonathan Muyal, Tao Hsu, and Pedro Padua

Characterization of Mg and Fe Contents in Nephrite Using Raman Spectroscopy
Xiaoyan Feng, Yong Zhang, Taijin Lu, and Hui Zhang













































































































































































































































































































































































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