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Eight natural-color pistachio pearls
Identification of “Pistachio” Coloured Pearls Treated by Ballerina Pearl Co.

A report on the colour treatment process for these intensely greenish yellow to yellowish-green cultured pearls and the techniques for identifying them.

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

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.

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Jaipur, India: The Global Gem and Jewellery Power of the Pink City

Examines Jaipur’s role as a coloured stone cutting and jewellery manufacturing centre, with profiles of 17 companies and their factory, trading and retail operations.

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A face-up view of a cushion cut diamond with blue color.
Article
Gems & Gemology’s 7 Most Unusual Encounters from 2019

Check out some of the most interesting and unusual diamonds and coloured stones submitted to GIA’s laboratories in 2019.

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A row of various shaped cut and polished pink diamonds.
Article
Why are Pink Diamonds Pink? GIA Researchers Dive Deep into their Crystal Structure

GIA researchers analysed more than 90,000 natural pink diamonds to better understand how these rare and beautiful diamonds formed and got their colour.

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The wax-impregnated bangle (left) showed bluish fluorescence under long-wave UV.
Strong Fluorescence in B-Jade Impregnated with Wax

A bangle is an example of the misconception that B jade is only impregnated by resin, when in fact wax-impregnated jadeite is also considered B-jade.

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Two white jade bracelets with dark color patches.
Nephrite Bracelet with Filled Cavity

A jade bracelet contains unusual fillers, used to create a smooth surface.

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These rubies were determined to be glass filled, partly due to the use of the DiamondView.
Separating Glass-Filled Rubies Using the DiamondView

The DiamondView instrument is able to identify glass as the filler in a pair of heart-shaped rubies.

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HPHT-treated blue diamond (left) with ragged-looking graphitization around an inclusion (center) and high-order interference colors with crossed-polarizing filters (right).
Large HPHT-Treated Blue Type IIb Diamond

Properties of, and theories on colour zoning exhibited by, the largest HPHT-treated blue diamond graded by GIA.

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This 20.60 ct specimen was purchased by the client as a “natural white pearl.”
Filled Pearl with Surface Features

A pearl, thought to be natural, is revealed to be a bead-cultured specimen with a pre-drilled nucleus.

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