Article Search Results

Reversible Colour Modification of Blue Zircon by Long-Wave Ultraviolet Radiation

Nathan D. Renfro, November 7, 2016

Determines whether blue zircon, inadvertently altered to brown by exposure to long-wave UV radiation, can be restored to its original colour through the use of incandescent light.

Fancy Dark brown to Fancy black Marange diamonds

Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions

Karen V. Smit, Elina Myagkaya, Stephanie Persaud, and Wuyi Wang, August 6, 2018

Characterises a suite of 40 natural brown to black diamonds from this deposit so that they can be distinguished from suspected treated black diamonds.

Iridescence in iris quartz from Jalgaon, India

Causes of Iridescence in Natural Quartz

Xiayang Lin and Peter J. Heaney, May 8, 2017

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

Karl Schmetzer, Franca Caucia, H. Albert Gilg, and Terrence S. Coldham, April 28, 2016

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

James E. Shigley, July 24, 2013

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

Yun Luo, July 24, 2013

How variations in UV lamp output can affect observed fluorescence colour and intensity.

Amethyst from Boudi, Morocco

Fabrizio Troilo, Abdelghani El Harfi, Salahaddine Mouaddib, Erica Bittarello, and Emanuele Costa, April 30, 2015

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

Thomas M. Moses, Mary L. Johnson, September 1, 2004

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

Shyamala Fernandes and Gagan Choudhary

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

Carolyn H. van der Bogert, Christopher P. Smith, Thomas Hainschwang, and Shane F. McClure

The Argyle diamond mine is the only known source of type IaB hydrogen- and nitrogen-rich diamonds coloured grey to blue to violet.

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