HPHT Diamond Update

Step 2: Advanced Gemology

Lesson 8

Synthetic Diamond History
High Pressure High Temperature

Diamonds were first synthesized from graphite in the 1950s by the high pressure high temperature (HPHT) process. In the mid-1980s the process was modified to create diamond film.

Chemical Vapor Disposition

Later chemical vapor disposition (CVD) improved diamond film production.

Diamond-Like Coatings

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

Current Uses

Cutting tools, optical windows for aerospace, infrared and X-ray instruments, microelectronics, coating for consumer eyewear and bar code readers, wear-resistant coatings for hard disks, read/write heads for videocassette recorders, audio recorders and disk drives.

Future Uses

Semiconductors for high speed computing, ‘cold’ cathodes for flat screen computer and video displays.

In 1999, General Electric introduced a new diamond treatment that can improve the color of some diamonds by several grades. The treatment caused considerable concern. If a J or M colored diamond can be improved to a D to G grade, how does one value it?

Another serious concern was how to identify the treated gems. Initially, there was no laboratory test that could identify them. In response to these concerns, GE agreed to mark …

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