Cubic zirconia, also known as Soviet stone, is a synthetic gemstone. It was first developed by the Soviets, hence the name Soviet stone. Also known as “cubic zircon” or “Soviet diamond”, it is a type of zirconium dioxide crystal. Zirconium oxide is mostly monoclinic crystals when it exists naturally, and mainly exists as the mineral “clinical zircon”. Zirconia, which exists as a cubic single crystal, is extremely rare in nature and can be synthesized artificially and is widely used as a substitute for diamonds.

Cubic zirconia, like diamond, is a cubic crystal. Under normal pressure, the stable crystal of zirconium dioxide is mono-clinic. Therefore, in the process of synthesizing cubic zirconia, a metal oxide with a molecular weight of 10 to 15% (usually yttrium oxide or Calcium oxide) as a stabilizer. Different production methods will add different amounts of stabilizers, so the physical and optical properties of cubic zirconia will be slightly different.

The density of cubic zirconia is quite high, with a specific gravity of 5.6 to 6.0. Its hardness is 8.5, which is lower than that of diamonds, but has surpassed most natural gemstones. Its refractive index is 2.15 to 2.18, and the surface has diamond luster. The dispersion index is 0.058 to 0.066, which is higher than that of diamonds. Cubic zirconia has no cleavage (Cleavage) and a conchoidal fracture, which is fragile. It shows yellow, yellow-green fluorescence under short-wave ultraviolet light, but not obvious under long-wave ultraviolet light.

  • How to Distinguish Diamond from Cubic Zirconia?

Since cubic zirconia was made in the mid-1970s, cubic zirconia has replaced all the raw materials for grinding fake diamonds because it has properties very similar to real diamonds. First of all, cubic zirconia has a refractive index of 2.17 and a dispersion of 0.06, which is very close to that of diamonds, and has the same homogeneity as diamonds. The hardness of cubic zirconia is as high as 8.5, which enables it to be inlaid on jewelry for long-term wear after being polished into gems, and will not be scratched and polished and lose its luster. Cubic zirconia can produce products with excellent transparency and completely colorless. In this way, after grinding it into a gem, its appearance is very similar to that of a diamond. It is said that in the first few years of production, using it as a real diamond made some experienced gemstone experts fooled.

There are still many differences between cubic zirconia and diamond; first of all, the hardness is not as good as diamond, and cubic zirconia is no exception lower than it. In addition, the specific gravity of cubic zirconia is as high as 5.6-6, which is 1.6-1.7 times that of diamond. If possible, use an instrument to measure the specific gravity, and you can immediately make a difference. The commodity code of cubic zirconia is CZ, therefore, fake diamonds ground with it are often called “CZ diamonds”. Because CZ diamonds are very cheap and look very similar to diamonds, they are welcomed by customers. Not only do ordinary people often wear jewelry with CZ diamonds, but also those who have real diamond jewelry. For safety, they also wear CZ diamonds. jewelry. The output of cubic zirconia is also increasing day by day. Only the United States has an annual output of more than 10 billion carats, which is the “jewel” cubic zirconia (CZ) created by 200 tons of cubic zirconia, also known as “cubic zirconia” “, “Soviet diamond” or “Soviet stone”, is a kind of zirconia (Zirconia, ZrO2) crystal. When zirconia occurs naturally, most of it is monoclinic crystals (mono-clinic), mainly in the mineral “Baddeleyite” (Baddeleyite). Zirconia, which exists in cubic single crystals, is extremely rare in nature, but it is often synthesized artificially and is widely used as a substitute for diamonds. Because this synthetic method was invented and first used in the Soviet Union, cubic zirconia is also called “Soviet Diamond” or “Soviet Stone”. Cubic zirconia is sometimes called “cubic zircon”, but this name is not entirely correct; because zircon (Zircon) is a kind of naturally occurring gemstone, its chemical composition is zirconium silicate (Zirconium Silicate, ZrSiO4), It is two different substances from synthetic cubic zirconia; and the cubic phase of zirconia is actually divided into two types: cubic crystal (Cubic) and tetragonal (Tetragonal).

Cubic zirconia is very close to diamond (diamond) optically, and most people may not be able to distinguish the two. But there are still some differences between the two under the microscope:
Dispersion: The dispersion of cubic zirconia is 0.060, which is higher than the 0.044 of diamond. So cubic zirconia appears to be more brilliant than diamond.
Hardness: Cubic zirconia has a Mohs hardness of 8.5 to 9.0, and diamond is 10.
Specific gravity: Cubic zirconia is 1.7 times heavier than diamond. But this feature can only be used to distinguish unset gems.
Flaws: The cubic zirconia produced is basically flawless inside and out. Natural diamonds are rarely completely flawless inside and outside.
Refractive index: The refractive index of cubic zirconia is 2.176, which is slightly lower than 2.417 of diamond.
Cutting: Due to the difference in refractive index, the cutting of cubic zirconia will be slightly different from that of diamond, which can be found by careful observation under a magnifying glass.
Color: Completely colorless diamonds are very rare, usually diamonds are light yellow. But cubic zirconia can be made into the highest grade of diamond, namely D grade color.
Heat transfer: The thermal conductivity of cubic zirconia and diamond is at two extremes. Cubic zirconia is an excellent thermal insulation material and can be used as a thermal insulation for jet engines. Diamond is one of the best thermal conductors, and its thermal conductivity surpasses copper. As long as the appropriate equipment is used, this property can best distinguish the two.

  • Cubic Zirconia of Different Colors

If different metal oxides are added to the raw materials, crystals of different colors can be obtained. For example:
Cerium: yellow, orange, red
Chrome: Green
Neodymium: Purple
Erbium: Pink
Titanium: Golden Brown
Some manufacturers also use different methods to improve their products, the most common is to add a layer of diamond-like carbon (DLC) on the surface of cubic zirconia by vapor condensation. The resulting product is harder than ordinary zirconia and looks more diamond-like. Another method is to spray a layer of metal oxide on the surface in a vacuum to make it bloom. But unlike plated with diamond-like carbon, this processing can be worn out.

For more information, you can also refer to Birthstone by Month: From January to December Cubic Zirconia vs Real Diamond