Driving a hybrid diamond?

The gemological community has recently been a buzz about the sale of so-called “hybrid diamonds” - a product we first encountered over five years ago but haven’t seen much of at NGL until just recently.

The stones recently received were identified as Cubic Zirconia (CZ), the most prevalent diamond substitute on the market, and available at less than a buck a carat. Our clients told us they had purchased synthetic diamonds - quite a different animal (mineral?) A true synthetic of diamond has the same basic chemical, physical and optical properties as a natural diamond (sounds like a definition, doesn’t it); it’s just grown in a laboratory. A CZ, or anything other than crystallized carbon does not qualify and is properly called a diamond substitute or imitation. The question then became, “Does this CZ have anything coating the surface?”

Let’s go back in time……

The first product we saw was marketed as an “amorphous diamond coating” over an undisclosed core stone. Since amorphous means non-crystalline, and diamond must be crystallized carbon, this is an obvious oxymoron regardless of what their supporting labs said. Being sold from our own backyard and documented by a local appraiser, we took interest and upon examination saw our old friend CZ. While the representative denied a CZ core, he finally relented and disclosed that yes, it was CZ, but with a proprietary overgrowth of diamond. If a coating was present it was beyond our methods of detection. We never really saw them for appraisal at the lab and I pretty much forgot of their existence other than the annoying fact that a local lab was providing paperwork and “graded” them with GIA standards as if they were a diamond. But, without a disgruntled client, I wasn’t about to “go after” anybody in this industry for just being misleading (I’d be up all night).

Fast forward……

Now, with our disgruntled client list growing and the gemological community questioning the process and its disclosure, we are in the middle of it.

I have been to a lot of gemological conferences in the past few years and the coating of stones has lately been a hot topic – not from an identification standpoint, but from their prevalence in the marketplace with exotic names and innovative marketing. (Topaz is given a layer of metallic ions and ouilá Mystic Topaz!) In the past few months, however gemologists around the world have been discussing the “diamond coating” topic and I harkened back to the old days thinking “So, what’s new?” Well, it turns out it’s the number of companies marketing this or a very similar product.

So, I put on my forensic gemologist hat and took a look at some of the leading
websites to see how they described their products. If, as a Graduate Gemologist and jewelry appraiser of thirty years I was having trouble deciphering their lingo, what must the consumer think? A problem I saw was different marketing interpretations on what I later found out to be the same product. Different brands had different disclosures and words like “diamond hybrid” seemed most prevalent. If I read them right, technology has provided us with the breakthrough of an inexpensive diamond-like product free from conflict and environmental concerns. The talk shows love this kind of stuff. No support of terrorists. No exploitation of the environment or little kids in Botswana. Nice.

But, remember class, a name placed before or after “diamond” means it’s either a really famous diamond or a FAKE. So back to the question, is there anything on the surface and if so, what is it? I contacted a few of the manufacturers to enlighten myself.

The first thing I found out was many of the brand names come from the same lab. I also discovered that some of the manufacturers don’t like each other very much and claim the “other guy” doesn’t even create a coating. While the process may vary (and one may claim a different substrate, one a middle layer, etc) the overgrowth is basically a process that I’ve been talking to my students about for years - chemical vapor deposition (CVD). CVD diamond was developed in the mid 1950’s and can now produce full-grown gem quality synthetic diamond crystals when grown upon a diamond seed crystal. When grown onto another material it is not truly crystalline but polycrystalline – without geometric alignment. This may lead to a diamond-like resistance to scratching and if composed of carbon, you can see the effort to call it a diamond-like coating (DLC). But, since the process cannot yet produce crystalline diamond, it is not transparent and as the coating gets thicker, the surface clouds – not a good attribute for a diamond substitute. So in order to not loose transparency, the layer must be incredibly thin – possibly on the order of nanometers (one billion to a meter) if not angstroms (ten billion to a meter) making detection virtually impossible.

The fact that a diamond coating has not yet been detected by some of the world’s best gemological laboratories makes it hard to rate this product as being coated at all. NGL does not have the expensive equipment to do chemical analysis (donors welcome), but a colleague with the same equipment the sellers claim to have been used to “prove” the process, detected no surface treatment whatsoever. To take his testing further, (where no gemologist should ever go) he tried to scratch the surface with a number nine hardness point (sapphire) which would have no impact if the surface was diamond-like. In fact, he obliterated every surface. So, are the testing labs the manufacturers employ to justify their product just getting a better-treated specimens than the public or are they reading something into their findings?

As I speak, bigger brains than mine are looking into how to address this product, but I am willing to share some personal views.

For sake of argument, let’s take the manufacturers at their word and put their product to the identification test for synthetic diamond. By definition, a synthetic has the same, physical, optical and chemical characteristics of the natural.

Physically. Diamond’s big number is 10 - its hardness. Claims as high as 9.8 for the deposited material drop to a resultant coating of 9.1-9.3 and some direct testing of released samples were scratched by sapphire (9). Strike one.

Optically. It would be interesting to compare the refractive index, (R.I.) but alas, that measurement has not been made or cannot be performed (even though at least one website claimed diamond’s R.I. for their product). And, since if grown to measurable thickness it is not transparent, it would certainly not be gem diamond. We would call that bort. Strike two.

Chemically. Diamond is essentially carbon. Additional elements, like nitrogen if present are in trace amounts. The manufacturers own reports show a high degree of non-carbon elements present, like Yitrium. Diamond has no Yitrium! If this is the CZ substrate being recorded, that itself shows insignificant coating. Strike three. But then you’re out of this game with just one strike.

Conclusion. I don’t have a problem with the sale of coated CZ. I have a problem with the way this particular product is being marketed - confusing some and downright misleading others. If people want to spend $100-500 for seventy-five cent CZ with the hope of an improved look or durability, they may do so. This is America. However, the purpose of an enhancement is to improve an aspect of the product. This is a fundamental question here. The technology certainly exists to make what is claimed, but because of its very nature, has their been an improvement? And, since the claim of “diamond coated” is erroneous what terminology is acceptable? The public is very familiar with the term “diamond”. We are trying to teach them what a “synthetic diamond” is. The confusion level on this product is unfair to the consumer and needs to be addressed. The term diamond-like coating may be adopted but needs to be proven to the satisfaction of the gemological community. Then, an affordable test that confirms treatment must be available or the consumer has to take the seller’s word for it and appraisers won’t touch it.

This brings me to the other major point to be discussed. Is the gemological community and the public OK with labs that first accept the seller’s statements and then apply terminology as if grading a diamond? Color, clarity and “equivalent” diamond weight? The sellers love to take this information for price comparisons. “If this were a natural diamond it would cost…”

When confronted with this several years ago, I didn’t see enough to raise any issues. Since the certifying labs are in my own backyard, I also didn’t want the appearance of bashing a competitor. When asked if interested in being one of those labs I have always declined. Many respected gemologists just shake their heads over this practice, but remember there are few legal rules for evaluating gems and jewelry. In the gray areas for now, gemologists can practice however they wish.

With full and accurate disclosure I say buy it if you like it. “Because it’s not your mother’s CZ, it’s Diamondzilla - new and improved with DLC!”


- Learn more about these and other diamond substitutes in our Diamond Grading class -