Deceptive Diamond Fluorescence: “Nothing is Always What it Appears”

Deceptive Diamond Fluorescence: “Nothing is Always What it Appears”

Bear Williams, laboratory director
Stone Group Labs

What If?
Consider yourselves on notice – If you are using Long Wave ultraviolet to identify natural diamonds from synthetic diamonds, looking for the N3 blue-white fluorescence, then you should read this, as your test may not necessarily be giving you the right answer. – gr

Deceptive Diamond Fluorescence
It is widely known that many natural diamonds show blue-white fluorescence when illuminated with Long-Wave Ultraviolet energy (LW-UV light). When blue-white fluorescence is seen, it is assumed that the diamond is of natural (Type Ia) origin, because this type of reaction indicates the presence of aggregated nitrogens (N3s and N4s) which, in natural diamond, takes millions of years to internally form.

In fact, says Williams, we even wrote about it here in the Roskin Gem News Report – Here – Fluorescence that proves Natural

Time to Reconsider
Now, after looking at and experimenting with coatings, Stone Group Labs wants us to step back and reconsider how we respond to blue-white fluorescence.

“Many of us use LW-UV fluorescence reactions to determine natural versus synthetic diamond – should the diamond show a good blue-white fluorescence. This fluorescence causes us to assume that we most likely have a natural diamond.” But to be certain of a “PASS,” notes Williams, “more gemologists are using instruments like MAGI-Lab’s EXA to get the definitive answers in effective screening. Having witnessed how visually effective such coatings are, we now recommend all stones be screened further, even those with blue-white fluorescence.”

Synthetic N3s?
Efforts have been made by synthetic diamond producers to introduce these aggregated nitrogens during synthetic growth in order to duplicate this natural diamond appearing photo luminescent (PL) reaction. These efforts have been met with very limited success and appear nonviable. [see Gem-A Journal of Gemmology, Volume 39(1), page 24 Gem Notes]

But what if blue-white fluorescence reactions using LW-UV could be observed in synthetics? “They could easily be mistaken for natural diamonds with quick visual identifications.” Recently, Stone Group Labs performed a series of experiments using acrylic monomers with photoinitiators (coatings).

(Fig. 1) This treatment was applied to lab grown diamond to produce the blue-white fluorescence.

Figure 1. CVD grown synthetic showing off blue-white fluorescence

“This treatment can be applied to the pavilion of, well, just about anything,” says Williams. In the following (Fig. 2) observe two cubic zirconias. “If you were using a LW-UV torch, and saw this type of fluorescence, would you immediately think that this is a common, garden-variety, natural diamond?” Maybe so.

Figure 2. Even CZ can be treated to show off the blue-white fluorescence and imitate natural diamond fluorescence

Nothing is ALWAYS What it Appears
“Never more true now this statement, as we look at what appears to be a natural diamond due to its blue-white fluorescence – but it is not natural. So we must ask (and we should always ask when testing a stone), what else could it be? What other tests need to be performed?” asks Williams.

“In the case of this experiment, the phosphors creating the blue fluorescence were applied on the pavilion of the stones as a coating. Tests were then run on MAGILab’s EXA equipment and the CVD diamond tested (of course) as a ‘FAIL’.”

Just to be Clear Here
This coating will not fool instruments that read the diamond’s spectra digitally, like the EXA, and like GIA’s iD100. And the professional labs will not be fooled. This coating will only fool the eye, and will be most problematic for the quick sight ID at the counter, checking for synthetic diamond, using just a LW-UV torch.

NOT Reliable
The purpose of this Lab Report release is to serve as a clear notice for those who may be dependent solely on using LW-UV LED penlights, violet lasers, or other long wave ultraviolet devices, in determining natural diamond authenticity – using the blue-white fluorescence reaction as proof positive. Such visual determinations are not reliable.

What the Future Holds
The product used for this study was not designed for durability, as it was experimentation only. It would not endure a steam cleaning, or alcohol based cleaners. However, please note that chemical vapor deposition technology using substrates with a 9.5 in hardness could be applied to protect the coating, and future development of CVD coatings incorporating a type of aggregated nitrogen is not without feasibility. – SGL