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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

Stuart Overlin, Brooke Goedert and Kellie Giordano, December 13, 2019

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

Cutting Diffraction Gratings to Improve Dispersion (“Fire”) in Diamonds

Al Gilbertson, Benjamin Gudlewski, Mary Johnson, George Maltezos, Axel Scherer, and James Shigley

A new microlithography process developed to create high-resolution diffraction grating patterns on portions of certain facets can improve the dispersion of light and thus the amount of “fire” in a diamond.

Coloured Diamonds in the Aurora Butterfly of Peace Collection

The “Type” Classification System of Diamonds and Its Importance in Gemmology

Christopher M. Breeding and James E. Shigley, June 1, 2009

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.

10 Study Samples Before and After HPHT Processing

GE POL Diamonds: Before and After

Christopher P. Smith, George Bosshart, September 1, 2000

This article explores and identifies the changes that type IIa GE POL diamonds experience before and after HPHT annealing.

A History of Diamond Treatments

Thomas W. Overton and James E. Shigley, March 1, 2008

Modern gemmologists and diamantaires are faced with a broad spectrum of colour and clarity treatments ranging from the simple to the highly sophisticated.

Synthetic Moissanite: A New Diamond Substitute

Kurt Nassau, Shane F. McClure, December 1, 1997

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 characterise it.

A New Lasering Technique for Diamond

Shane McClure, John M. King, June 1, 2000

Several diamonds were treated for the purposes of observation and report with a new laser technique which does not show the typical surface-reaching drill hole.

“Fluorescence Cage”: Visual Identification of HPHT-Treated Type I Diamonds

Inga A. Dobrinets and Alexander M. Zaitsev

HPHT-treated type I diamonds of various colours may exhibit unusually intense fluorescence at the facet edges and junctions.

Spectroscopic Evidence of GE POL HPHT-Treated Natural Type IIA Diamonds

David Fisher and Raymond A. Spits, March 1, 2000

Results from spectroscopic analyses of GE POL high-pressure high-temperature (HPHT) annealed nominally type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar appearance and type.

Abstracts; Spring 1991

Dona M. Dirlam

This article, from the Spring 1991 issue of Gems & Gemmology, is a compilation of abstracts of important gemmology-related articles published outside of Gems & Gemmology.

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