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'Cobalt-Blue' Gem Spinels
'Cobalt-Blue' Gem Spinels

Similarities between natural spinels — with intense blue color — and synthetic material, have led to difficulties in the recognition of the natural stones by traditional methods.

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The Early History of Gemstone Treatments

The author has uncovered many ancient references to the simulation or enhancement of gemstones.

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Cobalt Glass as a Lapis Lazuli Imitation

The properties of a novel gemological imitation, cobalt glass.

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The GEM DiamondMaster and the Thermal Properties of Gems

Thermal properties and the potential applications of the GEM DiamondMaster in testing them.

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The Jade Enigma

An examination of the various simulants of of nephrite and jadeite, and how to separate them from jade.

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Hornbill Ivory

The author reviews the nature of this material and some of the forms into which it has been fashioned, as well as means of identifying hornbill ivory from other ivories and from imitations.

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A Simple Approach to Detecting Diamond Simulants

Contrasting the physical properties of diamond with colorless specimens to identify the most problematic diamond simulants.

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Synthetic Moissanite: A New Diamond Substitute

Synthetic moissanite is much closer to diamond in overall appearance and heft than any previous diamond imitation; this article reports on how to identify and characterize it.

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Cubic Zirconia: An Update

An examination of the skull-melting technique used to produce cubic zirconia, first introduced in 1976, as well as the market status of this diamond simulant and information about its production and quality.

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shell pearl necklace, bracelet, earrings
Shell Pearl as a Pearl Imitation

Examination of commercially-available "shell pearls" reveals imitation material.

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