Uncommon Parallel Color Zoning in a Chameleon Diamond
A diamond examined in the Carlsbad lab shows chameleon coloring in an unusual pattern.
Wollastonite in Devitrified Glass Imitating Horsetail Inclusions in Demantoid Garnet
A yellowish green specimen with horsetail-like inclusions is found to be glass rather than demantoid garnet.
トラピッチェのようなブラジル産アメシスト (英語)
Twelve-Rayed Star Sapphire from Thailand
A black star sapphire produced from eastern Thailand, showing both golden and silver rays, is studied at GIA’s Bangkok lab.
D-Color Natural IIa Diamond with Walstromite Inclusion
A diamond is proven to have a superdeep origin through an inclusion of CaSiO3-walstromite.
カラーストーンのカットの品質：考慮するべき点
Part 5 of 5 in the series “Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond)” explores craftsmanship’s bearing on cut quality.
価値に影響を与えるために相互に作用するカラーストーンの要因
Part 4 of 5 in the series "Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond)" digs deeper into cutters’ choices and explores additional factors used in the trade to assess relative value.
Merelaniite Inclusions in Tanzanite
recently identified mineral is found, in whisker-like form, in a gem-quality tanzanite host.
カラーストーンの暗さと明るさ
Part 3 of 5 in the series “Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond)” examines how cutting decisions can have a profound effect on a gemstone’s color quality.
宝石のカッティングスタイル - 定義
Part 2 of 5 in the series “Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond)” establishes a common language for discussing cutting styles, with a focus on basic faceting styles, and offers a short discussion on cabochons and beads.
Large HPHT-Treated Blue Type IIb Diamond
A look at the color zoning exhibited by the largest HPHT-treated blue diamond graded by GIA.
Gemstone Guidebook Project
A project coordinated by GIA and the NGO Pact provides a valuable educational tool to women miners in Tanzania.
Natural Blue and Black Diamonds, a Byzantine Garnet Intaglio, Yogo Sapphires, and “Kasumiga Pearls”
An overview of the Summer 2018 Gems & Gemology content.
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.
モンタナ州のYogo（ヨゴ）渓谷から産出されたサファイアの宝石学的な特徴 (英語)
A look at the mining and distinguishing characteristics of this naturally vibrant blue sapphire.
合成ダイヤモンドの特徴 (英語)
Presents a visual guide to the growth processes and major gemological spectroscopic features of synthetic diamonds.
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.