For centuries, rubies have captivated humanity with their vivid red color and seductive beauty. They are very precious gemstones and are used in all forms of jewelry. However, as technology has advanced, lab-made rubies have entered the market, making it necessary for both consumers and jewelers to be able to distinguish between natural and synthetic rubies. In this article, we will explore in detail the characteristics and methods of distinguishing real rubies from artificial rubies.
True ruby nature
colour
The most distinctive color of rubies is a deep and vivid red. However, natural rubies can have a range of hues in the red spectrum. They may have dark shades of pink, purple or even orange. The color is usually unevenly distributed within the stone, with areas of deep red and light red. For example, natural Burmese rubies may have a rich pigeon blood red color and are highly sought after. This natural color change is due to the presence of different trace elements and the geological conditions under which rubies are formed.
distinct
Most natural rubies have some inclusions. These could be tiny crystals of other minerals, rutile needles, or cracks. Inclusions are often irregular in shape and size. For example, a ruby from Thailand may contain rutile inclusions like silk, which can give the stone a certain appearance when enlarged. The presence of these inclusions is actually a sign of natural origin, as lab-made rubies are often more flawless or contain very different types of inclusions.
hardness
Ruby is a type of mineral corundum with a Mohs hardness of 9. This high hardness makes them extremely durable and scratch-resistant. When a real ruby rubs against a piece of glass, it easily scratches the glass, while the ruby itself remains unscathed. This property is one of the key identifiers of true rubies, as many other red gemstones have lower hardness levels.
Refractive index
The refractive index of a true ruby is between 1.76 and 1.77. This means that when light enters a ruby, it bends in a specific way. Jewelers use tools such as refractometers to measure this property. The way light is reflected and refracted in natural rubies can create beautiful colors and unique glories.
Properties of lab-made rubies
Color uniformity
Lab-made rubies are usually more uniform in color. Because they are produced in a controlled laboratory environment, conditions can be adjusted to achieve a consistent shade of red. They lack the natural ribbon common to true rubies. For example, an artificial ruby may be completely uniform red all over the stone, without any visible change in hue or intensity.
Lack of typical inclusions
Synthetic rubies usually do not contain the natural inclusions found in real rubies. They may have some inclusions, but are usually different in nature. For example, they may have tiny bubbles or growth patterns that are characteristic of the synthetic growth process. These inclusions tend to be more regular and symmetrical than the random and diverse inclusions found in natural rubies.
Production method and its characteristics
Flame melting method
This is a common way of making rubies. In this process, powdered alumina (the main component of corundum) is melted in a high temperature flame. The resulting synthetic rubies often have curved growth lines or streaks that can be seen under magnification. These growth lines are a sign that the flame has fused to form a ruby.
Hydrothermal process
Here, rubies are grown in high-pressure, high-temperature water solutions. Synthetic rubies produced by this method may have a more crystalline appearance and different types of inclusions related to the hydrothermal growth environment, such as small particles of the growth medium.
The Chakralski method
In this technique, seed crystals are dipped into a molten material and slowly pulled upward as the crystals grow. Synthetic rubies made by the Zocralski process may have characteristic patterns of dislocations and inclusions related to the drawing process.
Differentiated test methods
Visual inspection
As mentioned earlier, looking at color uniformity and the presence of inclusions can give an initial indication. A jeweler with a trained eye can usually spot differences in color distribution and inclusions type. For example, if the ruby looks too perfect and the color is consistent, it may arouse suspicion. However, visual inspection alone is not always decisive.
Magnification
Using a loupe or a microscope, jewelers can closely examine the internal structure of the ruby. They can look for the specific types of inclusions mentioned above. The magnification can also help in detecting the growth patterns and lines in lab-created rubies. For instance, a 10x loupe can reveal the presence of tiny bubbles or the curved growth lines in a synthetic ruby that might not be visible to the naked eye.
Refractometer Testing
By measuring the refractive index of the ruby, a jeweler can compare it to the known values for natural and synthetic rubies. If the refractive index is outside the range of a natural ruby, it is likely a synthetic or a different gemstone altogether. However, some advanced synthetic rubies may have refractive indices close to that of natural ones, so this test should be used in conjunction with other methods.
Spectroscopy
Spectroscopic analysis can provide detailed information about the chemical composition and the absorption spectra of the ruby. Natural rubies have specific absorption bands due to the presence of trace elements like chromium and iron. Synthetic rubies may have different absorption patterns or lack some of the characteristic bands. For example, a natural ruby might show strong absorption in the blue and violet regions of the spectrum, while a synthetic ruby produced by a particular method might have a different spectral signature.
UV Fluorescence
When exposed to ultraviolet light, both natural and synthetic rubies can exhibit fluorescence. However, the intensity and color of the fluorescence can vary. Natural rubies from different regions may have different fluorescence characteristics. For example, some Burmese rubies may show a strong red fluorescence, while synthetic rubies may have a weaker or different colored fluorescence. This test can be a useful additional tool in the identification process.
Conclusion
Distinguishing between real rubies and lab-created ones requires a combination of knowledge, experience, and the use of various testing methods. Understanding the properties of natural rubies, the characteristics of synthetic ones, and being able to apply the appropriate testing techniques is essential for anyone involved in the jewelry trade or for consumers looking to purchase a genuine ruby.
Whether it is through visual inspection, magnification, refractometer testing, spectroscopy, or relying on gemological certificates and reputable jewelers, taking the time to ensure the authenticity of a ruby is crucial. With the increasing sophistication of synthetic gemstone production, the need for accurate identification is more important than ever to protect the value and integrity of the ruby market and to ensure that consumers get what they pay for.
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