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Star rhodochrosite from the Sweet Home mine, Colorado
Colored Stones and Pearls

Abstracts of speaker presentations from the “Colored Stones and Pearls” session of GIA’s 2018 International Gemological Symposium.

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CLIPPIR diamond from Angola’s Lulo mine
Gem Characterization

Abstracts of speaker presentations from the “Gem Characterization” session of GIA’s 2018 International Gemological Symposium.

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Single-crystal CVD diamond
New Technologies and Techniques

Abstracts of speaker presentations from the “New Technologies and Techniques” session of GIA’s 2018 International Gemological Symposium.

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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 through 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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Pearl farm on the Indonesian island of Lombok
Bead-Cultured and Non-Bead-Cultured Pearls from Lombok, Indonesia

Documents the retrieval and testing of P. maxima cultured pearls from a Lombok hatchery.

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Aurora effect in iris agate.
Aurora Iris Agate

An iris agate with a unique growth texture is carved to produce an aurora-like effect.

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Color bars on top and sides of 3,019 ct rough opal
The Challenges of Cutting a Large Gem Opal Rough

A first-person account of cutting a 3,019 ct piece of white opal to create a 1,040 ct gem with play-of-color across the surface.

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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 colored stones.

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

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

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