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A blue synthetic star sapphire from past production of Wiede’s Carbidwerk
Synthetic Star Sapphires and Rubies Produced by Wiede’s Carbidwerk, Freyung, Germany

Details the process used by Wiede’s Carbidwerk to produce star synthetic corundum from the mid-1950s until the 1970s.

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Iridescence in iris quartz from Jalgaon, India
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.

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15 ct tanzanite
Pleochroism in Faceted Gems: An Introduction

Describes the phenomenon of pleochroism and its complex effect on the appearance of coloured stones.

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Blue amber beads from the Dominican Republic
Colour Phenomena of Blue Amber

Investigates the presence of fluorescence, rather than iridescence, as the cause of colour in blue amber from the Dominican Republic and Indonesia.

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Optimising Face-Up Appearance in Coloured Gemstone Faceting

How contrast patterns can increase perceived brightness and optimise a gemstone's appearance.

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A History of Diamond Treatments

Modern gemmologists and diamantaires are faced with a broad spectrum of colour and clarity treatments ranging from the simple to the highly sophisticated.

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Treated-Colour Pink-To-Red Diamonds from Lucent Diamonds Inc.

Using a multi-step process, Lucent Diamonds has developed a new treatment process for certain natural diamonds that creates colours from pink-purple to red to orangey brown.

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Modelling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Fire, and More about Brilliance

This second major article in a three-dimensional modelling study analyses fire – the visible extent of light dispersed into spectral colours.

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Classifying Emerald Clarity Enhancement at the GIA Gem Trade Laboratory

One of the greatest concerns with emerald filling is the degree of clarity enhancement such treatment represents

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The Identification of Zachery-Treated Turquoise | Gems & Gemmology

Millions of carats of turquoise have been enhanced by a proprietary process called the Zachery treatment.

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