Cubic zirconia is a popular diamond substitute that closely resembles a real diamond in appearance. However, there are several key differences between the two that can help you distinguish one from the other. Whether you are a jewelry enthusiast, a potential buyer, or simply curious about gemstones, understanding these differences is essential. In this article, we will explore various methods and characteristics to tell a cubic zirconia from a real diamond.
Visual Inspection
Clarity
A real diamond often has some internal inclusions or flaws, even if they are very small and difficult to see with the naked eye. These inclusions can be in the form of crystals, feathers, or other imperfections. When using a jeweler’s loupe or a magnifying glass with at least 10x magnification, you can usually spot these internal features.
In contrast, cubic zirconia is typically more flawless. It is manufactured in a way that results in a much higher degree of clarity. So, if a stone appears completely free of any inclusions under magnification, it is more likely to be cubic zirconia rather than a real diamond. For example, a natural diamond might have a tiny pinpoint inclusion that is only visible under close inspection, while a cubic zirconia will seem perfectly clear.
Cut
The cut of a diamond has a significant impact on its sparkle and brilliance. A well-cut diamond has precise and symmetrical facets that refract light in a beautiful and consistent manner. When you look at a real diamond, it creates a lively and dynamic play of colors as the light bounces off the various angles of the cut.
Cubic zirconia can also be cut well, but it often has a different pattern of light refraction. It may have a more “flashy” or “disco ball” like effect, with a more pronounced and somewhat artificial-looking dispersion of light. The light refraction in a cubic zirconia is not as complex and natural as that of a real diamond. For instance, a real diamond’s sparkle is more like a soft, continuous glow with a wide range of colors, while a cubic zirconia might have a more concentrated and intense burst of color in certain spots.
Color
Most diamonds have a natural color range that goes from colorless to a faint yellow or brown tint. The more colorless a diamond is, the rarer and more valuable it is. However, real diamonds rarely have a pure, vivid white color.
Cubic zirconia, on the other hand, is often produced to have a very bright, white color that can seem almost too perfect. If a stone has an extremely white and uniform color without any hint of natural tint, it is more likely to be cubic zirconia. Additionally, some cubic zirconia may be available in a wide range of colors, including vivid blues, pinks, and yellows, which are less common in natural diamonds and usually only found in very rare and expensive fancy colored diamonds. For example, a diamond with a very slight yellowish hue is more in line with a natural diamond, while a stone with a bright, icy white color is suspect of being cubic zirconia.
Physical Properties
Hardness
Diamonds are the hardest known natural substance. They rank a 10 on the Mohs scale of hardness. This means that a real diamond can scratch almost any other material. You can perform a simple scratch test, but it should be done with extreme caution as it can damage the diamond if it is real. Try to scratch the stone gently with a hard object like a piece of quartz or a sapphire. If the diamond gets scratched easily, it is definitely not a real diamond.
Cubic zirconia has a hardness of around 8.5 on the Mohs scale. While it is still relatively hard, it is not as hard as a diamond. So, if a supposed diamond is scratched by a material that a real diamond should be able to resist, it is likely cubic zirconia. However, this test is not always conclusive as some synthetic diamonds and other diamond simulants may also have a relatively high hardness.
Density
The density of a diamond is approximately 3.52 grams per cubic centimeter. To measure the density, you would need to weigh the stone accurately and then use a displacement method to measure its volume.
Cubic zirconia has a higher density, around 5.6 to 6 grams per cubic centimeter. If you have the means to measure the density of a stone and it is significantly higher than 3.52, it is probably cubic zirconia. But this method requires specialized equipment and is not practical for most people without access to a gemology lab.
Thermal Conductivity
Diamonds have a very high thermal conductivity. A diamond tester, which works on the principle of detecting the rate at which heat is conducted away from a heated probe, is often used. When the probe touches a real diamond, the heat is quickly dissipated, and the tester gives a positive reading.
Cubic zirconia has a much lower thermal conductivity. It will not conduct heat away from the probe as quickly as a diamond. However, some synthetic diamonds and moissanite can also have thermal conductivity values that are close to a diamond’s, so this test alone is not always definitive. For example, moissanite can sometimes give a false positive on a basic diamond tester, so it’s important to use this test in conjunction with other methods.
Other Tests and Considerations
Fog Test
Gently breathe on the stone as you would on a mirror. A real diamond will disperse the heat from your breath very quickly and will not fog up. If the stone fogs and takes a while to clear, it is likely cubic zirconia. This is because diamonds have high thermal conductivity compared to cubic zirconia. For instance, a cubic zirconia may fog up and stay fogged for several seconds, while a diamond will clear almost instantly.
UV Light Test
Some diamonds fluoresce under ultraviolet (UV) light. Place the stone under a UV light source and observe. While not all diamonds fluoresce, and the intensity of fluorescence can vary, a real diamond may show a faint blue or other color fluorescence.
Cubic zirconia may also fluoresce, but the color and intensity are usually different. It might have a stronger, more yellowish or greenish fluorescence. So, if a stone shows a very bright and unusual fluorescence color under UV light, it could be cubic zirconia. However, this test is not conclusive as some synthetic diamonds can also have unique fluorescence characteristics.
Price Consideration
Real diamonds have a significant cost associated with them based on their quality, size, and other factors. If a stone is being sold at a price that seems too good to be true, it is very likely cubic zirconia or another imitation. Do some research on the market prices of similar diamonds to get an idea of the expected cost. For example, a large, seemingly high-quality diamond being sold at a fraction of the price of a comparable real diamond is a major red flag.
Professional Appraisal
If you are still unsure after performing some of the above tests, it is advisable to take the stone to a professional jeweler or a gemological laboratory. They have access to advanced equipment such as spectrometers, which can analyze the chemical composition and light absorption properties of the stone. A professional appraisal will provide a definitive answer and can also give you information about the quality and value of the stone if it is a real diamond.
Conclusion
Distinguishing a cubic zirconia from a real diamond requires a combination of visual inspection, understanding of physical properties, and sometimes the use of specialized tests. While no single method is completely foolproof, by carefully examining the clarity, cut, color, hardness, density, thermal conductivity, and other characteristics, as well as considering price and getting a professional appraisal if needed, you can make a more accurate determination. Being able to tell the difference between these two gemstones is important not only for making informed purchasing decisions but also for appreciating the unique qualities of real diamonds and their value in the world of jewelry.
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