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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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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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GIA’s Symmetry Grading Boundaries for Round Brilliant Cut Diamonds

A presentation of parameters used to support GIA's symmetry grading system.

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Possible “Sister” Stones of the Hope Diamond

A recent study compares a specially created model of the Hope diamond with recent computer models of the French Blue to determine if other stones could have resulted from either recutting.

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GemCad View of the French Blue Enclosed Within the Tavernier Blue
A Crystallographic Analysis of the Tavernier Blue Diamond

This study uses both historical information and modern data to create a computer model of the Tavernier Blue, orienting the finished diamond within the original diamond crystal.

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Computer Rendering of the “French Blue” Diamond
The French Blue and the Hope: New Data from the Discovery of a Historical Lead Cast

With the use of modern tools and technology, this article sheds light on the history and provenance of both the French Blue and the Hope diamonds.

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Colour Grading “D-to-Z” Diamonds at the GIA Laboratory

This article discusses the history and ongoing development of GIA's colour grading system, and explains how its laboratory applies it.

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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.

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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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Modelling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Brilliance

A mathematical model which can analyse how appearance factors depend on proportions.

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