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.
Optical defects in diamond: a quick reference chart
A simple chart of optical defects in diamond, including those that produce colouration and fluorescence colours.
Fluorescence produced by optical defects in diamond: measurement, characterisation and challenges
How variations in UV lamp output can affect observed fluorescence colour and intensity.
Amethyst from Boudi, Morocco
An introduction to Moroccan amethyst, which features distinctive color zoning and inclusions.
A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds
The GIA diamond cut grading system described here includes the components of brightness, fire, scintillation, polish and symmetry, as well as weight and durability concerns, into a single overall grade for cut quality for standard round brilliants.
Gem-Quality Andalusite from Brazil
Widely known as a rock-forming mineral, andalusite is not frequently encountered as a gem material.
Grey-To-Blue-To-Violet Hydrogen-Rich Diamonds from the Argyle Mine, Australia
The Argyle diamond mine is the only known source of type IaB hydrogen- and nitrogen-rich diamonds coloured grey to blue to violet.
Hibonite: a New Gem Mineral
A 0.23 g orangey brown crystal, a 0.39 ct step-cut gem.