Nitrogen or Not?

Gary Roskin, G.G., FGA -- JCK Online, 2/1/2001 2:00:00 AM

General Electric, developer and owner of the high-pressure, high-temperature (HPHT) "Pegasus process" that turns brown Type IIa diamonds into white Bellataire diamonds, claims that Type IIa diamonds contain no nitrogen. But according to research carried out by the Gübelin Gem Lab in Lucerne, Switzerland, Type IIa stones do contain nitrogen, albeit in infinitesimal amounts. In fact, GGL researchers say it's the nitrogen-as reconfigured by GE's HPHT process-that allows brown diamonds to be turned white.

Why does nitrogen matter? Until recently, Bellataire diamonds had been touted as "naturally pure." But all gem diamonds are essentially pure carbon. So to imply that Bellataire diamonds are pure and other diamonds aren't is not quite correct, but it's certainly understandable.

It takes only a minute trace of an element such as nitrogen, boron, or hydrogen to create a colored diamond. Yellow diamonds, for example, have a tiny but measurable amount of nitrogen (1,000-3,000 parts per million) and are classified as Type I diamonds. For many years, because the amount of nitrogen in other diamonds was so small-20 or fewer parts per million or even parts per billion-research scientists regarded the amount as "insignificant." Because of this nearly pure state, such diamonds were claimed to be "pure carbon" and classified as Type IIa.

We now understand that it's because of nitrogen that Type IIa brown diamonds can be changed to colorless. Thus, the once "insignificant" nitrogen is now the most significant part of the Pegasus equation.