Rare and valuable minerals

How to distinguish a black diamond from a black cubic zirconia?

Cubic zirconia is often called an artificial diamond. This is not entirely true: in its chemical composition, diamond is a cubic allotropic form of carbon, while cubic zirconia is zirconium dioxide. It was obtained by Soviet scientists from the Physical Institute of the Academy of Sciences. Lebedev (FIAN) for the creation of laser equipment. But it turned out that the brilliant mineral found its calling in a completely different area – jewelry. From his progenitor-institute he received only a name. Since the 90s, cubic zirconia has been actively used in the production of jewelry. Which caused quite a lot of difficulties for ordinary people: after all, it is not always possible to visually distinguish a precious stone from an artificial mineral.

How to distinguish cubic zirconia from a diamond

Method 1: looking for “defects” using a magnifying glass

Natural stones always have small inclusions. Gemologists distinguish 4 types of these: points, clusters of points, voids and feathers. You can see them when the stone is magnified 10 times or more. Artificially created cubic zirconia does not have any inclusions.

Method 2: consider the cut

When cutting diamonds, it is very important to make the edges as even, sharp and symmetrical as possible: the play of light in the stone depends on this. Cubic zirconia also shines with less demanding cuts. If you look at the mineral through a magnifying glass with 10x magnification, you will notice rounded edges. Gemologists say they are “double.” Also, an experienced jeweler or gemologist can distinguish the play of light in these stones. But for the average person, alas, this may remain unnoticeable.

Method 3: checking wettability

If you drop vegetable oil on a stone, it will flow smoothly over the diamond. While on cubic zirconia it will separate into drops or blots. This is due to the fact that the ability of a diamond to be wetted by dense liquids is high, while that of its artificial counterpart is, on the contrary, low. This method can be called one of the safest, which will help distinguish a diamond from cubic zirconia in a ring or earrings.

Method 4: checking thermal conductivity

Due to the fact that diamond and cubic zirconia have different thermal conductivities, you can find out which stone is in front of you by breathing. You need to breathe on it in much the same way as when you are trying to warm your hands. Diamond has high thermal conductivity and will not fog up. But condensation (“evaporation”) will appear on the surface of the cubic zirconia.

Method 5: testing for hardness

Almost everyone knows that natural diamond is incredibly hard. If you scratch it on the glass (or vice versa with the glass on a diamond), a visible scratch will remain on the glass. In the case of cubic zirconia, the stone itself will suffer, so we recommend using this method only as a last resort. Pay attention! Never hit rocks. A natural diamond is durable, but can break quite easily.

Method 6: testing for electrical conductivity

Electrical conductivity testing is carried out using a special tester (duotester). Cubic zirconia conducts electricity, while diamond is a dielectric. The tester records this and gives a completely unambiguous answer.

Method 7: checking the glow in ultraviolet

We do not recommend checking stones with ultraviolet light: in some sources you can read that a natural diamond will not glow in UV rays, but cubic zirconia will. This is wrong. Natural diamonds can also glow in ultraviolet light if they contain certain impurities. Gemologists even distinguish several different groups of diamond fluorescence – from very strong to none. It is noteworthy that in different countries different stones are of greater value: in the USA they prefer luminous diamonds, and in Europe – without fluorescence. Finally, the surest way not to make a mistake and purchase a real diamond is to buy it only in trusted places where a certificate is attached to the product. Thus, all diamonds and jewelry with inserts presented in our showroom have the appropriate papers from the independent gemological center of Moscow State University. The certificate contains information about the cut shape, weight of the diamond, color group and clarity. And using a unique number and a link to a report from the laboratory, you can confirm the authenticity of the information and the stone itself. You can view the diamonds you are interested in in our catalog: A diamond is a true aristocrat among stones, especially if it is distinguished by high clarity and high-quality cutting. Natural diamonds of pure water are very expensive, and if we are talking about stones of rare shades (for example, blue, green or red), then their price is measured in hundreds of thousands, or even millions of dollars. There are a lot of scammers around diamonds, like other valuables. Royal stones are counterfeited very often, and sometimes you can only determine whether it is a diamond or an imitation in a laboratory. It’s one thing when you consciously buy an analogue of a diamond simply because you can’t afford the original; it’s another thing when they sell you a fake for a significant amount of money, deceiving you in the most unscrupulous way. The topic of our conversation today is how to distinguish a diamond from other stones and other analogues.

Diamonds as they are

Diamonds are cut gem quality diamonds. This means that they are large enough (from 0,1 carats), transparent, have a minimum of flaws and are suitable for cutting, that is, they can be used for the production of jewelry.

During cutting, a diamond loses at least half its weight. There are special programs that allow you to choose the optimal cutting method for a particular specimen.

Chemically, diamonds are pure carbon, that is, they are close relatives of ordinary graphite (as in a simple pencil). However, over millions of years, under favorable conditions, carbon undergoes a magical transformation, turning into a transparent sparkling mineral of wondrous beauty. It is the hardest substance on Earth and is considered the standard on the Mohs scale. Diamond is not such a rare mineral, but gem-quality stones are rare, which determines their fabulous cost. Small and cloudy diamonds are widely used in industry, for example, in the creation of cutting tools. Diamonds are mined on almost all continents except Antarctica. Rich deposits have been discovered in Africa (Botswana, South Africa, Angola), Canada and Russia. At the moment, Russia is the recognized leader in the extraction of gem-quality minerals. Yakut diamonds are famous throughout the world!

The world’s diamond reserves are gradually depleting. Their replenishment is not expected, because the age of natural minerals ranges from 100 million to several billion years!

Diamond analogues

  • Synthetic diamonds. Attempts to create an artificial diamond were made a long time ago, but were crowned with success only in the middle of the last century. The technology for producing jewelry synthetic diamonds is complex and expensive, so at the moment they are only 15-20% cheaper than their natural counterparts.
  • Synthetic minerals. The most popular among the minerals of this group are cubic zirconia and moissanite (the latter are significantly more expensive). Visually, they are very similar to diamonds, quite hard, but they differ in a fundamentally different formula and physical characteristics.
  • Imitations. This group includes both cheap natural minerals (topaz, zircon, rock crystal) and all kinds of rhinestones (including the famous Swarovski crystals).

Natural diamonds are a great investment. There are fewer and fewer of them in nature, and they are constantly rising in price. The cost of synthetic diamonds, on the contrary, is decreasing: technologies are improving and becoming cheaper.

How to distinguish a diamond from cubic zirconia

A diamond differs from a cubic zirconia in its entire essence, expressed in a chemical formula. If the formula of diamond is simply C, that is, carbon, then the formula of cubic zirconia is ZrO2 (zirconium dioxide). They are often called zirconium or zircons, which is incorrect: the first is a metal, the second is a natural semi-precious yellow mineral.

Cubic zirconias are very similar to diamonds, but differ from them in optical properties, have more rounded edges and not so outstanding hardness. They are widely used not only for jewelry purposes, but also replace diamonds in other areas where strength of as much as 10 on the Mohs scale is not needed.

Cubic zirconia is a development of the Soviet Lebedev Physical Institute. Lebedeva, who blew up the jewelry market in the 1970s. But scientists just wanted to get an inexpensive artificial crystal with special properties suitable for creating laser-based equipment!

The cost of cubic zirconia is decreasing day by day, which makes it possible to use it even in costume jewelry. Unfortunately, it is often used to deceive gullible buyers who want to purchase diamond jewelry at a low price.

By experimenting with additives, cubic zirconia of various shades is obtained. We have learned to imitate even the rarest polychrome alexandrite, which costs fabulous money!

The easiest way to distinguish cubic zirconia from a diamond in a ring by eye is to simply breathe on the stone. If it fogs up, then you are guaranteed not to have a diamond.

There are other ways to distinguish these minerals without resorting to laboratory analysis:

  • Fat test. Place a little vegetable oil on the stone. On a diamond the drop will remain intact, on cubic zirconia it will disintegrate.
  • Optical properties. Place the stone on the printed text. If the letters are readable through it, then it is cubic zirconia.
  • Shine. Cubic zirconia shines almost as brightly as diamond, but produces a multi-colored spectrum. The brilliance of the diamond is silvery with yellowness, in monochrome.

Despite the universality and general availability of these verification methods, they are sometimes uninformative for the amateur. Therefore, you should refrain from purchasing expensive jewelry second-hand and from unauthorized retail outlets.

If you consciously buy jewelry with cubic zirconia abroad, then most likely it will have the CZ marking on it. If you are deliberately misled, there will be no identifying marks.

Differences between moissanite and diamond

Let’s consider another analogue of the “king of stones”, moissanite. It is silicon carbide and has the formula SiC.

Natural moissanite was first discovered at the end of the last century in Arizona. Its discoverer was the French chemist Ferdinand Moissan, who christened the new mineral with his own name.

As it turns out, there is very little natural moissanite on Earth: it is found mainly in the remains of meteorites. As a rule, there are small pebbles that do not have a diamond shine and transparency. The largest nuggets found did not exceed a few millimeters in diameter.

Almost at the same time, Edward Atcherson patented a technology for the synthesis of powdered SiC, which was used primarily in the production of abrasives. It was a synthetic carborundum material, chemically a complete analogue of moissanite.

The invention of the technology for synthesizing jewelry-quality carborundum produced a real revolution. Jewelers received an almost complete analogue of a diamond, which is more than an order of magnitude cheaper than its noble counterpart. However, even synthetic moissanite is much more expensive than cubic zirconia.

Natural moissanite is negligible. So don’t trust sellers: you won’t find jewelry with this naturally occurring mineral. But carborundum is a permanent resident of jewelry store shelves.

It is almost impossible to distinguish moissanite from a diamond at home, at least not for a specialist. All methods that can be applied without the use of special equipment lead to damage to moissanite or require the presence of a natural diamond as a sample.

You can recognize a diamond next to a moissanite by its more subdued shine: the second shines brighter due to its higher refractive index. Moissanite is equally transparent, very refractory, and resistant to aggressive chemicals. Its hardness ranges around 9 on the Mohs scale. This means that it can be scratched with a diamond, but not with anything else.

If you don’t mind the stone, you can perform a basic thermal test. Apply the flame of a match or lighter to the diamond and moissanite. Both stones will become smoky, but if the diamond appears in its original form after cleaning the carbon deposits, the carborundum will turn green and become cloudy.

How to distinguish a real diamond from a fake

Almost any piece of glass can be cut like a diamond, but this will not turn it into a noble diamond. However, this is sometimes enough to deceive a gullible buyer, attracted by a very tempting price.

A diamond weighing 0,25 carats costs at least 60 thousand rubles. A half-carat diamond is valued at three times more expensive. And if we are talking about flawless and larger specimens, the price jumps by an order of magnitude or more!

There are many ways to distinguish a diamond from glass or other types of fakes. The rougher the imitation, the sooner inconsistencies are identified. So grab your magnifying glass and take a look at:

  • Cut. The diamond has perfectly smooth, clear edges, without rounding or the effect of double rays. Between the lower and upper parts of the diamond (“pavilion” and “crown”) there is a kind of girdle, a girdle. It should be slightly rough to the touch.
  • Flaws. Yes, the fewer flaws a stone has, the higher it is valued, but nature does not tolerate faceless perfection. A natural diamond will definitely show some flaws (turbidity, dots), while an artificial crystal will be perfect.
  • Scratches. As mentioned above, diamond is the hardest substance on Earth. A priori, it cannot have micro-scratches or other damage. The glass can be scratched instantly, even with a nail file. This test is not indicative only for moissanite.
  • Transparency. A diamond is transparent, but due to its high refractive index, you will not be able to see anything through the stone – you will only see a shining point. You can even read through cubic zirconia and glass.
  • Range. A diamond scatters rays in a white or slightly yellowish spectrum. Each face casts only one ray. Most diamonds exhibit a bluish glow when exposed to ultraviolet light. But there are also exceptions.
  • Frame. Diamonds set in silver, and even more so, jewelry alloys, are nonsense. Only gold of at least 585 standard or platinum!
  • Fastening. No jeweler would use a setting to hide the “pavilion” ring, that is, the lower part of a large diamond. Cubic zirconias and glass usually bashfully hide their rears. They are often attached with glue, which is unacceptable for diamonds.

It is impossible to distinguish a natural diamond from an artificial one at home! Artificial diamonds (not imitations, but complete analogues) have the same elemental composition, chemical and physical properties as natural ones.

You can distinguish a diamond from glass by resorting to the simplest tests, many of which were mentioned in the appendix to cubic zirconia. This is, first of all, a fogging test: the surface of the diamond does not fog up or traces of breath evaporate in the blink of an eye.

The “drop” test is also indicative: a drop of oil or water on the surface of the diamond does not spread. In addition, a diamond remains cool for a long time even when squeezed in the hand, while fakes immediately take on the temperature of the human body.

A little about certification

There are many ways available to check whether the diamond you are looking at is real or imitation, but none of them can give an absolute guarantee. Even experts can only distinguish cheap fakes at first glance, in other cases using laboratory research methods.

The authenticity of the stone is established after a series of tests carried out in accordance with the protocol. The optical characteristics of the stone are checked and it is carefully examined in various lighting conditions and environments using electronic equipment.

Each natural diamond receives a certificate indicating its characteristics. The most authoritative are the GIA certificates issued by the Gemological Institute of America. HDR and AGS certificates are highly rated.

Private companies often offer certification services at a more affordable price than the above organizations, but you should not always trust them. It is unlikely that they will award a certificate of authenticity to an outright fake, but they can easily “play” with the characteristics of the stone.

Russia has its own certification system and institutions that evaluate precious stones. Certificates are issued in Russian and contain a “portrait” of the stone, as well as information about its characteristics and personal number.

Russian legislation requires mandatory indication of the characteristics of the stone insert when selling jewelry. So if you buy jewelry in a store, you can determine from the tag what your diamond can “boast” of.

No non-specialist can determine the origin of a stone with absolute accuracy, and, unfortunately, forgery of certificates is not uncommon. So if you can afford high-end jewelry, do not buy it from dubious places. Diamonds and savings are incompatible concepts!

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