In the mid-1970s, zirconium oxide (ZrO2) was produced in Russia, specifically at the Lebedev Physical Institute in Moscow, which, despite the new materials discovered in recent years, remains, even today, one of the best and most widespread imitations of Diamond. 
Thanks to a particular chemical mixture, zirconium oxide is stabilized in the cubic crystalline system from which it takes the name CZ ("cubic zirconia"). 
The method for synthesizing it is called "skull melting method" and in the trade it is known by various names depending on the country that produces it. Zirconia in the United States, Finite and C-Ox in Russia, Djevalite in Switzerland and KSZ in Germany.
CZ should absolutely not be confused with Zircon which is a mineral, even of gem quality, but with completely different characteristics.
Today, unfortunately, often and mistakenly, many use the term "zircon" to mean any colorless stone that sparkles and wants to imitate a diamond.
Just to give an idea of ​​how convincing CZ is as an imitation of Diamond, just think that 60 million carats of it are currently produced per year. 
It is often found mounted in cheap jewelery on bracelets, necklaces, earrings, etc.
We prefer not to do this and only sell jewelry with natural diamonds but there are many jewelry stores that routinely sell jewelry with CZ. And there is absolutely nothing wrong if the customer is clearly informed in advance. 
As is well known, the brilliance and luster of diamonds reach very high levels, and despite this, cubic zirconia comes very close to them. 
Its light dispersion coefficient is then only slightly higher (0.060 compared to 0.040). Its hardness on the Mohs scale is between 8 and 8.25 which are more than good values ​​to ensure that it is used in jewelery and mounted without even many precautions.
Its specific weight, however (ouch, ouch) is much higher than that of Diamond (5.50/6.00 compared to 3.52) and this already opens a large gap in the possibility of easily distinguishing between one and the other. 'other. 
Cubic Zirconia, of equal dimensions, will always weigh, more or less, 40 percent more than a Diamond.
Another simple way of separating it from the Diamond is the so-called "see through".

The CZ, when cut "round brilliant", like many of the Diamond imitations (including those we examined above) has a wider critical angle than the Diamond itself so much of the light hitting the pavilion (the cone-shaped lower part) does not remain in the gem but comes out of it so, for example, if we place it face down on a book, we can see the printed characters through it, which on the contrary we cannot do with the Diamond because in the latter it is precisely the exceptional quantity and quality of the light (apart from the terrible cuts that go beyond the standards) so to speak "trapped in the stone" that prevents this from happening.
However, these two methods have a limit: they can only help if the CZ is loose and not mounted on a jewel. 
When at the end of the 70s and beginning of the 80s, Cubic Zirconia began to forcefully invade the market, it created quite a few apprehensions among the majority of jewelers and potential buyers.
Not as much as Moissanite which we will talk about shortly but enough to cause concern in the world of jewellery.

Consider that (this also applies to many diamond imitations) as CZ has a very low cost it is cut without any consideration for the waste of the rough and therefore the cut will always be optimal, if not excellent. 
And for the same reason you will always find it clean and free of significant inclusions, which is not always possible with Diamond due to its high cost since every rough material judged potentially to be gem quality (the rough pieces that are not are destined for industry) are optimized as much as possible. The cutter, in the case of a Diamond, will always have as the ultimate goal of his work the highest possible economic profit which almost always (although not always) coincides with the maximum optimization of the mass, or the weight of the finished Diamond.
If a cutter, just to give an example, to maintain as much weight as possible in a Diamond leaves a part of the rough unpolished and polished (the so-called "natural") or adds an extra facet ("extra facet") it is obvious that these "imperfections" will have their weight in the final judgment of the cut with consequent loss of value but if in this way he will have obtained a 2.00-carat stone as an alternative to a 1.99-carat one where the difference in economic terms is substantial to be compensated the cut is largely not optimal, you can be sure that he will always opt for this solution.
All precautions and attentions that the cutter of a CZ can easily do without given the large quantity and quality of raw material available.
It is for these reasons that, paradoxically, it sometimes happens that the cut of an imitation is "better" than that of the Diamond itself.

You understand well how a CZ mounted on a jewel, new and freshly polished, with the edges and corners not yet worn, constitutes a problem, even for the expert. 
Yes, of course no imitation will ever have the luster of a faceted Diamond and no imitation will ever have the corners of the facets as sharp as those of the Diamond but who is that professional, that trader or that jeweler who, no matter how expert, will feel like come up with a few thousand euros based on these elements alone which are only indicative and not diagnostic.
Fortunately, however, technology intervened to restore some order and above all to deal a hard blow to CZ.
Very shortly after CZ had invaded the market, the Thermal Tester also known as Thermal Probe or, more simply, Thermal Pen was created.
A brilliant idea also because it is based on a very simple physical principle: Thermal Conduction.
Thermal Conduction of a gem is the degree to which the surface of the gem changes in response to a specific amount of heat. Diamond is one of the things that stays cold the longest when hit by a heat source. And this, among other things, is one of the reasons why diamond finds such wide use in space components.
As we were saying, the operating principle of the Thermal Pen is very simple.
The tip of the Thermal Pen, resting lightly on the gem, transmits heat to it and then measures how much it heats up. The separation between Diamond and imitations occurs because the former disperses heat much faster than other gems and its surface remains colder.
The results are then simply read on a display.

The Thermal Pen works very well with CZ and with all the other diamond imitations but not (or at least not as many manufacturers would have you believe) with Moissanite.
If, as we said above, CZ caused a strong shock upon its release in the field of precious stones in general and jewelry in particular, you must imagine that what Moissanite produced was a real earthquake. 
The entire press covered it extensively and for a long period in the jewelry world it seemed like nothing else was being talked about.
Moissanite is currently the best, most credible and most successful imitation of Diamond.
Chemically speaking, Moissanite is a silicon carbide and owes its name to the French chemist, winner of the Nobel Prize, Henri Moissan, who first discovered this rare mineral (along with some microscopic diamonds) inside the meteorite “Canyon Diablo ” in Arizona in 1904. 
This even though synthetic Moissanite was produced in large quantities as early as 1893 and was known by the name of "Carborundum" used above all for its excellent qualities as a semiconductor and as an abrasive.

All the imitations of the Diamond that we have seen so far, you will have noticed, also present similar aspects compared to the Diamond but they all have something that clearly and definitively differentiates them from the latter.
Synthetic Spinel, synthetic Corundum and YAG have a significantly lower brilliance distinguishable even with the naked eye, synthetic Rutile and Strontium Titanate have a very low hardness and too much dispersion (fire), CZ and GGG have a high specific weight and the latter also has a low hardness.
Synthetic Moissanite no.
It is the closest thing there can be to Diamond in terms of refractive index (only a little more): specific weight (only a little less than Diamond);  high hardness (9.25 on the Mohs scale); dispersion coefficient of white light (only slightly more than in Diamond).
But what is really striking about synthetic Moissanite is its general appearance when placed next to a Diamond. 
To date, there is no other imitation that can even come close to it in terms of credibility.
Yet it too, Moissanite, has its "Achilles heel". 
Something that totally differentiates it from Diamond and that allows it to be separated with relative ease. 
This something has a name and it's called birefringence.
When a beam of light hits any material the speed of the photons changes and as it changes its direction also changes accordingly.
When light passes from air to any material, in addition to decreasing its speed (apparently because in fact the speed of light does not change), it also changes direction due to the phenomenon of refraction. In some materials (this depends on the crystalline system) it still proceeds with a different but single direction while in others it proceeds in two different directions. In practice it doubles.
In Diamond the ray of light, although broken, so to speak, proceeds in a single direction while in other systems (and this is the case of our Moissanite) it divides in two.

This is due to the fact that Diamond is monorefringent (you might, in fact, hear that "it often has anomalous birefringence" but this has nothing to do with what we are talking about now) and Moissanite on the contrary is birefringent. 
This in fact involves the doubling of the facets and the reflection of the belt detectable under the microscope but also with a simple ten-fold magnification lens. 
With just one precaution.  Moissanite is almost always faceted (even with fraudulent intent, unfortunately) with the optical axis perpendicular to the table and therefore looking at it in this direction it will not present any doubling and it will seem like you are looking at a diamond.
However, all you have to do is tilt it so that from any other angle it shows the classic split.
One final consideration. Synthetic Moissanite, as we were saying, upon its release on the market in 1996, created quite a stir in the market especially considering the fact that it was considered difficult to identify.
Before then, as we said above, jewelers could use thermal resistance testers, the thermal pen, easily available on the market, with complete peace of mind, to separate the diamond from all the other imitations.
With this new material it was no longer possible to do so as the resistance and thermal conductivity values ​​of Diamond and synthetic Moissanite are almost the same.
This was, all things considered, the real reason (combined with the astonishing verisimilitude) that created so much amazement, why Moissanite was so widely covered in the specialist and non-specialist press.
Has anything changed since then? Listening to the opinions of the various manufacturers of the new "Thermal Testers", everything has changed. Now the "new" Testers are able to separate Moissanite from Diamond. It's written on the displays: Moissanite on one side and Diamond on the other, each with its own sound and color. Everything is fine then, has Moissanite stopped scaring us?
Well, that's not really the case. For the reason that these tools (which among other things cost several hundred euros each) simply don't work. 
Or rather (which in our opinion is even worse) they don't always work. They are not reliable, to put it bluntly.
A jeweler or trader who decides to rely only on the Thermal Pen to separate Diamonds from Moissanites (but rest assured that no serious professional does this) would risk not only money but, even more seriously, his reputation. 
In any case, what we always recommend, in these cases, is to contact a specialist in the sector.
Unless you are one yourself.

Category: