Pleochroism and Color Change in Faceted Alexandrite: Influence of Cut and Sample Orientation
Shows how alexandrite’s color and color change are affected by cut and the orientation of table facets.
The Color Origin of Gem Diaspore: Correlation to Corundum
Examines the color origin of color-change diaspore, known commercially as Zultanite, and compare the effectiveness of the chromophores it shares in common with corundum.
Natural-Color Pink, Purple, Red, and Brown Diamonds: Band of Many Colors
Summarizes data collected by GIA on more than 90,000 natural diamonds in this color range and presents their gemological and spectroscopic properties.
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.
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.
Natural-Color Green Diamonds: A Beautiful Conundrum
Characterizes diamonds with exceptionally rare natural green color, based on GIA’s extensive database of samples.
Iridescence in Metamorphic “Rainbow” Hematite
Analyzes the substructures that cause the intense iridescence observed in “rainbow” hematite from Minas Gerais, Brazil.
The Very Deep Origin of the World’s Biggest Diamonds
Explores an exceptional family of diamonds, referred to as “CLIPPIR” (Cullinan-like, Large, Inclusion-Poor, Pure, Irregular, and Resorbed), that formed in a superdeep environment.