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Suite containing over 36 carats of Yogo sapphire
Gemological Characterization of Sapphires from Yogo Gulch, Montana

A look at the mining and distinguishing characteristics of this naturally vibrant blue sapphire.

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A bright orange, multi-faceted gem.
Article
Fall for Autumn Gems

Nature gives us a brilliant palette of color-changing leaves and a spectacular kaleidoscope of colorful sunsets during the fall season.

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Kasumigaura pearl necklace and recently harvested nucleated pearls
Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics

Examines Japanese “Kasumiga” freshwater cultured pearls, which grow in a variety of colors.

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Fancy Dark brown to Fancy black Marange diamonds
Black Diamonds from Marange (Zimbabwe): A Result of Natural Irradiation and Graphite Inclusions

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

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Recently discovered and legendary diamonds in the blue/gray/violet color range
Natural-Color Blue, Gray, and Violet Diamonds: Allure of the Deep

Summarizes data collected on more than 15,000 natural blue/gray/violet diamonds examined by GIA during the last decade and examines the mechanisms that produce this color range.

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Grading the Hope Diamond

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

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Article
Famous Diamonds Examined by GIA

An aura of mystery has always surrounded these natural wonders, so it was quite an honor when GIA researchers examined these famous diamonds.

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Bursts of yellow and purple radiate throughout this round cut amertrine.
Article
Colorblocking: The Art and Fashion of Multicolor Gemstones

The fashion trend of colorblocking can be found in the artistic combinations of color in multicolor gemstones known for their color zoning or banding.

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Paula Crevoshay’s “Yogo Columbine” sapphire pendant
The Role of Silicon in the Color of Gem Corundum

Considers the previously unreported but critical impact of silicon on the coloration of gem-quality sapphire.

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Vanadium and Chromium-Bearing Pink Pyrope Garnet: Characterization and Quantitative Colorimetric Analysis

This type of pink pyrope garnet, believed to have been mined in Tanzania, shows a distinct color-change phenomenon resulting from its unique chemical composition.

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