Step 2: Advanced Gemology

Lesson 8

Early Responses to HPHT Diamond Treatments

Initially, no laboratory tests could identify HPHT diamond treatments. In response to concerns in the jewelry trade, GE agreed to mark the girdle facet of their treated diamonds with the inscription “GE POL.”

However, since this inscription was very shallow, it could be removed with no apparent loss of gem weight. The Gemological Institute of America (GIA) Gem Trade Laboratory reported a number of gems with the inscriptions removed. In addition, other labs were soon treating diamonds with the same process and not inscribing their gems with the GE trademark. At least six companies from the US, China, Japan, and Russia began using the HPHT process.

Because of the fiscal impact of this treatment on the trade, several major laboratories began examining the treated stones.

A Brief History of Synthetic HPHT Diamonds

Diamonds were first synthesized from graphite in the 1950s by the HPHT process. In the mid-1980s, the process was modified to create diamond film. Later, chemical vapor disposition (CVD) improved diamond film production.

In the mid-1990s, diamond-like coatings (DLC) improved on CVD, requiring less temperature and less energy.

Currently, HPHT diamond has numerous…