Step 5: Advanced Gem Information

Lesson 2

Synthetic diamonds aren’t new. General Electric (GE) has been making them for over half a century. Most of the diamond abrasives we use are GE synthetics. However, creating gem-grade diamonds costs more than mining them. Thus, few are produced.

In 2003, we saw the introduction of new types of synthetic diamonds. Most manufacturers reliably make their disclosures. However, some resellers don’t, since they know most small diamonds never go to a lab. In this article, we’ll cover how to identify CVD, HPHT, and NPD synthetic diamonds.

To learn more about identifying natural diamonds, read about their inclusions.

CVD Diamonds

Chemical vapor deposition (CVD) diamonds come in sizes up to 3 carats, with a normal range of inclusions.


You can identify CVD diamonds fairly simply. They have a unique strain pattern that doesn’t resemble that of natural diamonds and strong red fluorescence. In addition, they lack the typical “Cape Line” at 415 nm on their absorption spectrum. Instead, they present a strong line at 737 nm.

HPHT Diamonds

GE developed the high pressure/high temperature (HPHT) method of growing diamonds. In 2003, a company called Gemesis (now…