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Diamonds: What’s your type?

Figure 7: Left: Type IIa diamonds have no detectable nitrogen or any other impurities. Right: Type IIb diamonds have one boron atom substitute for a carbon atom.

It is important to note, however: just because a diamond does not fluoresce does not mean it has less nitrogen. The Type IaA aggregate can quench fluorescence, which means it is entirely possible to have a high-nitrogen diamond that does not fluoresce. It is also important to note that fluorescence alone is not diagnostic of natural or laboratory-grown growth of a diamond, but it can be a clue. Laboratory-grown diamonds and treated diamonds can fluoresce; however, strong blue ‘N3’ fluorescence can be a good indicator of a natural diamond.

Laboratory-grown diamonds are usually one of three types: Type IIa, Type IIb, or Type Ib.

Scenario II: Determining if a diamond has nitrogen

In the next example, you are presented with a D-Z diamond, which you are purchasing from an off-the-street client. You want to know if the diamond is Type IIa to determine if you need to send it to a laboratory for additional testing.

A short-wave ultraviolet (SWUV) transparency tester can provide you with quick insight as to whether the diamond is Type IIa. Indeed, desktop diamond spotters can quickly show you if a diamond is transparent to SWUV.

In a nutshell

Diamonds are typed by the presence or absence of nitrogen impurities. Type I diamonds have nitrogen; Type II diamonds do not. The sub-classifications depend on the way the nitrogen or other impurities are arranged in the diamond’s crystal lattice.

Type IaA, Type IaB, and Type Ia diamonds have been in the Earth’s mantle for much longer than diamonds with single nitrogen. This is an important distinction when it comes to laboratory-grown diamonds, which are created over days or weeks and do not have the Type IaA or Type IaB aggregates. Laboratory-grown diamonds have a finite set of diamond Types they can be grown as: Type IIa (no nitrogen, no other impurities), Type IIb (boron), and Type Ib (single nitrogen).

Diamond type tells us a lot about the diamond, from the relative conditions of its formation to its cause of colour. Having a baseline knowledge of what it means can help you make determinations about the next best steps for testing. Ultimately, understanding diamonds at the atomic level is not just for laboratory gemmologists anymore—all industry professionals should educate themselves on the subject.

Figure 8: A diamond with medium or stronger blue fluorescence is likely mined (not laboratory grown). This is because the N3 centre causing the fluorescence requires extreme heat and billions of years to form. This process has not yet been replicated in a laboratory.
Image courtesy GSI

Alethea Inns, BSc., MSc., GG, is a fellow of the Gemmological Association of Great Britain (FGA). Her career has focused on laboratory gemmology, the development of educational and credentialing programs for the jewellery industry, and the strategic implementation of e-learning and learning technology. Inns is chief learning officer for Gemological Science International (GSI). In this role, she leads efforts in developing partner educational programs and training, industry compliance and standards, and furthering the group’s mission for the highest levels of research, gemmology, and education. For more information, visit

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