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.
Dual-Color Double Stars in Ruby, Sapphire, and Quartz: Cause and Historical Account
Examines a form of asterism comprising two six-rayed stars, one white and one that exhibits the stone’s bodycolor. Firsthand accounts and a survey of patent documents reveal that diffusion has been used to create or enhance this optical phenomenon in synthetic and possibly natural corundum since the 1950s.
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.
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.
Causes of Iridescence in Natural Quartz
Describes the occurrence of iridescence, and the role of differential etching, in quartz crystals from India’s Jalgaon District.
Reversible Color Modification of Blue Zircon by Long-Wave Ultraviolet Radiation
Determines whether blue zircon, inadvertently altered to brown by exposure to long-wave UV radiation, can be restored to its original color through the use of incandescent light.
Chrysoberyl from the New England Placer Deposits, New South Wales, Australia
Examines a collection of chrysoberyl samples from these sapphire placer deposits to determine their distinct mineralogical and chemical properties.
Amethyst from Boudi, Morocco
An introduction to Moroccan amethyst, which features distinctive color zoning and inclusions.
Pleochroism in Faceted Gems: An Introduction
Describes the phenomenon of pleochroism and its complex effect on the appearance of colored stones.
Optical Defects in Diamond: A Quick Reference Chart
A simple chart on optical defects in diamond, including those that produce coloration and fluorescence colors.