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The Wittelsbach Blue

This article describes what is known about the Wittelsbach Blue since it was first reported in 1666, and the gemmological information released to date on this diamond.

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Hydrogen-rich Diamonds
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.

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Coloured Diamonds in the Aurora Butterfly of Peace Collection
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.

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Characterisation and Grading of Natural-Colour Pink Diamonds

Known for their great beauty and rarity, pink diamonds have long been sought after by jewellers, collectors and consumers.

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Grading the Hope Diamond

One of the most popular exhibits at the Smithsonian Institution, the stunning Fancy Dark greyish blue Hope diamond was formally graded by GIA’s gem laboratory.

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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 of Coloured Diamonds in the GIA Gem Trade Laboratory

How GIA’s Gem Trade Laboratory grades coloured diamonds, including an expanded colour grading terminology, is explained.

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Characterisation and Grading of Natural-Colour Yellow Diamonds

A large number of natural-colour yellow diamonds are analysed using grading and appearance aspects among other characteristics to clarify the differences between them and the light yellow diamonds associated with GIA's D-to-Z colour grading scale.

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Characterising Natural-Colour Type IIB Blue Diamonds

More than 400 blue diamonds were studied at the GIA Gem Trade Laboratory over several years to reveal additional information about the relationships between their colour, clarity and other gemmological properties.

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An Important Exhibition of Seven Rare Gem Diamonds

The stories behind seven strikingly beautiful rare natural diamonds, united in an exhibit at the Smithsonian, are told here.

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