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Gem-related Field
How Does It work?
Sapphires' captivating allure and vivid tints have captivated humanity for centuries. In the realms of jewelry and embellishment, these precious gemstones are in high demand due to their association with royalty and elegance. Nevertheless, as the gemstone market expands and technological advances enable the production of lab-grown and imitation gemstones, distinguishing natural sapphires from their synthetic or counterfeit counterparts has become a pressing challenge.

This article explores the intriguing world of sapphire identification, revealing the scientific techniques and gemological knowledge used to distinguish between natural sapphires, lab-grown varieties, and synthetic stones. We examine the intricacies of visual examination, refractive index measurements, and spectroscopy techniques in an effort to unravel the secrets hidden within these extraordinary gemstones.
At first, it is difficult to distinguish a natural gemstone from a synthetic one, but there are a number of subtle ways to determine whether or not you are holding a genuine stone.
Use Your Eyes!
It all starts by visually examining natural sapphires' distinguishing characteristics, mesmerizing hues, and inherent flaws that attest to their organic origin. The growth patterns, inclusions, and distinctive characteristics of natural sapphires, which distinguish them from their synthetic counterparts, will be revealed later.

If you have ever held a sapphire in your hands, you must have noticed that loupe-clean sapphires with wonderful hues are extremely uncommon. The majority of natural sapphires have dark areas, color zoning, and inclusions. Yet, lab-grown do not. Even with the most advanced advancements in lab-grown gemstones, sapphires are typically loupe clean with a very clear, uniform blue color.

Inclusions such as needle-like rutile inclusions (also known as silk), fingerprints, and color zoning are typically present in sapphires that are formed in nature. The existence of these inclusions is evidence of the sapphire's natural formation. However, due to the controlled manufacturing process, lab-grown sapphires and imitations may exhibit fewer inclusions or appear remarkably spotless.

The natural sapphire on the left has a sparkling peacock blue hue that is nearly impossible to replicate in lab-grown sapphires. The one on the right is made of synthetic material and is uniformly blue with a tiny window.
The capacity of sapphire to transmit light is used to evaluate its transparency. Natural sapphires can range from translucent to transparent, allowing light to interact with the gem's intrinsic characteristics. Synthetic sapphires and imitations can occasionally have a transparent or plastic-like appearance, lacking the natural transparency of natural stones.

Although carat size alone cannot determine the authenticity of a sapphire, it should still be taken into account. Natural sapphires are found in various sizes, with larger specimens being relatively uncommon and commanding a higher price. Yet, note that lab-grown sapphires can be produced in various sizes, including larger carat weights. Actually, you are most likely purchasing a synthetic one if you buy a loupe-clean sapphire for a fraction of its price. There is no such thing as "a cheap price" in perfect stones. Loupe clean sapphires over 1 or 2 carats will almost always be sold with a lab certificate that can guarantee their true nature.

Last but not least, I would say that lab-grown sapphires frequently have a slightly "off" hue in comparison to natural blue sapphires. It can be difficult to determine if you are not a gemologist, but a quick glance at other sapphires will make it obvious.
The pair in the middle is synthetic. See how the blue color in synthetic stones is slightly "purplish" and does not reflect the true essence and authenticity of a blue sapphire (royal blue on the left and blue on the right)
This last point may be noteworthy but less pertinent if you are unfamiliar with the gemstone world. Natural sapphires are always cut to retain as much weight as possible, particularly for larger specimens, whereas synthetic cuts are frequently perfect regardless of the size of the stone.

They can also be cut with various fancy cuts for larger specimens, which skilled gemstone cutters will decline to do so as to avoid wasting the natural sapphire's weight.
Let's Get a Closer Look!
The origin of a sapphire can be determined by analyzing inclusions, growth patterns, and other microscopic characteristics. Typical development characteristics of natural sapphires include fingerprints, rutile inclusions, and hexagonal growth patterns. Synthetic sapphires may exhibit growth characteristics such as curved growth lines or gas bubbles that are uncommon in natural sapphires.

Also, synthetic sapphires may exhibit consistent and uniform growth, devoid of the inherent flaws found in natural stones.
These lab-created stones contain inclusions in the form of straight lines that are never found in natural sapphires.
These parallel lines will always indicate that the stone is not natural.
Refractive Index Measurement
Refractive index is a fundamental property of gemstones that can be used to differentiate natural sapphires from lab-created or synthetic ones. Typically, the refractive index of sapphire occurs within a specific range (between 1.76 and 1.78). By using a refractometer, gemologists can measure the refractive index of a sapphire and compare it to the known values for natural sapphires. Typically, synthetic sapphires have higher refractive indices than natural sapphires due to disparities in their chemical composition or growth techniques.
Spectroscopy techniques are widely employed in gemstone identification, including detecting sapphire origin. The two most commonly used spectroscopic methods are:

a. UV-Visible Spectroscopy: Natural sapphires often exhibit characteristic absorption bands in the ultraviolet (UV) and visible spectrum. These absorption bands are caused by trace elements in the crystal lattice, such as iron (Fe) and titanium (Ti). Synthetic sapphires may have different absorption patterns or lack these characteristic bands, allowing for differentiation.

b. Infrared (IR) Spectroscopy: IR spectroscopy can provide valuable information about the molecular structure of a sapphire. Natural sapphires exhibit specific absorption features related to aluminum-oxygen (Al-O) bonds. Synthetic sapphires, especially those produced by the Verneuil or flame fusion method, may show additional absorption peaks or different peak intensities.

Natural VS. Synthetic
Magnetism and Sapphires
In the majority of natural blue sapphires, there is also "surplus" iron, primarily Fe3+. The graph shows that this excess iron can also be detected with a spectrometer. In synthetic sapphires, there is no detectable "excess" iron and only a negligible quantity of iron in the Fe2+-Ti4+ charge transfer; consequently, there is no magnetism.

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Benjamin Poudevigne
Social Media Manager at GemMatrix
With over ten years of marketing experience, I finally decided to settle down in Bangkok to work in an area that I have always been interested in: the gemstones industry. I'm still learning how the market works on a daily basis, and I enjoy sharing my experience with those who are interested in learning more about gems in general.