Skip to Main Content
Skip Nav Destination

High-pressure-high-temperature treatment of gem diamonds

James E. Shigley
High-pressure-high-temperature treatment of gem diamonds
Elements (March 2005) 1 (2): 101-104


Annealing of gem-quality diamonds at very high pressures (above 5 Gpa) and temperatures (above approximately 1800 degrees C) can produce significant changes in their color. Treatment under these high-pressure-high-temperature (HPHT) conditions affects certain optically active defects and their absorptions in the visible spectrum. In the jewelry industry, laboratory-treated diamonds are valued much less than those of natural color. Polished diamonds are carefully examined at gemological laboratories to determine the "origin of color" as part of an overall assessment of their quality. Currently, the recognition of HPHT-treated diamonds involves the determination of various visual properties (such as color and features seen under magnification), as well as characterization by several spectroscopic techniques. HPHT-treated diamonds were introduced into the jewelry trade in the late 1990s, and despite progress in their recognition, their identification remains a challenge. While some detection methodologies have been established, the large number of diamonds requiring testing with sophisticated analytical instrumentation poses a logistical problem for gemological laboratories.

ISSN: 1811-5209
Serial Title: Elements
Serial Volume: 1
Serial Issue: 2
Title: High-pressure-high-temperature treatment of gem diamonds
Author(s): Shigley, James E.
Affiliation: Gemological Institute of America, Research Department, Carlsbad, CA, United States
Pages: 101-104
Published: 200503
Text Language: English
Publisher: Mineralogical Society of America and Mineralogical Society of Great Britain and Ireland and Mineralogical Association of Canada and Geochemical Society and Clay Minerals Society, International
References: 26
Accession Number: 2005-041378
Categories: General geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: International
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200515
Close Modal

or Create an Account

Close Modal
Close Modal