Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions
Characterises a suite of 40 natural brown to black diamonds from this deposit so that they can be distinguished from suspected treated black diamonds.
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.
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 coloured stones.
Optimising Face-Up Appearance in Coloured Gemstone Faceting
How contrast patterns can increase perceived brightness and optimise a gemstone's appearance.
Fluorescence produced by optical defects in diamond: measurement, characterisation and challenges
How variations in UV lamp output can affect observed fluorescence colour and intensity.
Optical defects in diamond: a quick reference chart
A simple chart of optical defects in diamond, including those that produce colouration and fluorescence colours.
The “Type” Classification System of Diamonds and Its Importance in Gemmology
Knowledge of type allows gemmologists to better evaluate if a diamond might be treated or synthetic, and whether it should be sent to a laboratory for testing.
The Impact of Internal Whitish And Reflective Graining on the Clarity Grading of D-To-Z Colour Diamonds at the GIA Laboratory
This article reviews the GIA Laboratory’s history of reporting on certain types of graining which are often the only characteristics present in large, high-clarity, high-colour diamonds.