Is Your Ruby Genuine Or Not?

A natural ruby is recognized first and foremost by the depth and intensity of its red color. Among the finest examples, the color is described in the trade as pigeon’s blood. This phrase refers to a rich, pure red that is both deep and bright at the same time. It should display an almost glowing quality, as though light is emanating from within the crystal. For gemologists, this quality is a delicate balance between tone, saturation, and the absence of distracting modifiers. Ideally, the red should remain consistent across the entire gem, without areas that appear paler, darker, or uneven. Stones with this kind of homogeneous distribution are rare and highly sought after.

Although rubies are fundamentally red (keep that in mind), variations in hue are common and depend largely on the deposit and trace element chemistry. Chromium is the key chromophore responsible for the red color, while iron and other elements can shift the tone toward orange, purple, or even brown. Rubies with a dominant pure red hue and just a slight bluish undertone are generally the most valuable. By contrast, stones with strong secondary hues such as orange or purple are considered less fine, though they can still be beautiful and collectible. Understanding the influence of geology and chemistry helps explain why rubies from different origins, such as Myanmar, Mozambique, or Madagascar, may show distinct personalities in their red.

When evaluating rubies, it is important to watch out for stones that appear overly bright, unnaturally vivid, or with a neon glow. While natural rubies can indeed fluoresce due to their chromium content, an exaggerated or artificial appearance may suggest the presence of treatments such as glass filling or dyeing, or in some cases, a fully synthetic stone. Natural rubies of high quality have a rich and powerful saturation of red, but the color always feels balanced and integrated with the crystal. They should not display distracting overtones of brown or gray, as these diminish both the aesthetic and the market value. Lower quality rubies may appear dull or somewhat muddy in color. It is important to emphasize that such rubies are still natural but sit on a lower tier of value compared to fine examples.

Consistency of color is another critical factor. High quality rubies should present an even distribution of red when viewed face up. Gemologists are particularly attentive to the phenomenon of color zoning, where the crystal shows areas of lighter or darker tones. Zoning can appear as angular patches or bands caused by uneven distribution of chromium during crystal growth. While zoning does not compromise the ruby’s authenticity, it does affect its appearance and can significantly lower its value. An evenly colored ruby demonstrates both rarity in nature and superior cutting, as lapidaries must orient the rough carefully to minimize zoning.

Natural rubies typically maintain their beauty across sunlight, fluorescent light, and incandescent light. Their fluorescence, caused by chromium, can make them appear more vibrant in daylight, sometimes giving the impression that the stone glows from within. Under incandescent light, the same ruby may take on a slightly purplish tone. These subtle changes are expected and even considered part of a ruby’s charm.

Artificially colored or synthetic stones, by contrast, often show unstable or unnatural behavior under varied lighting, sometimes appearing too bright in one condition and lifeless in another. The ability of a ruby to maintain a strong and balanced red under multiple light sources is one of the hallmarks of fine quality.

Natural and synthetic rubies glow when exposed to ultraviolet light. Some rubies glow less than others (like Thai rubies), but it also doesn't mean they are fake! Usually, synthetic rubies tend to glow more than natural ones. In other words, some rubies glow more depending on their geological formation.

(Ex: Burmese ruby will display a strong or medium-strong red color under longwave and shortwave UV light)

Natural rubies often fluoresce under UV light, emitting a red, orange, or sometimes purple glow. This reaction is due to the presence of chromium in the ruby, which causes it to absorb UV light and then re-emit it at a visible wavelength.

Once again, the degree of fluorescence can vary depending on the ruby's origin and the specific trace elements present. For example, rubies from some locations like Myanmar (Burma) are known for strong fluorescence, while others may have a weaker response. Depending on their creation method and additives, synthetic rubies may have a different fluorescent response than natural rubies. Some synthetic rubies may not fluoresce at all, while others may exhibit an intense but distinctly different glow.

Please note that, while useful, the UV light test is not definitive on its own. Some natural rubies may not fluoresce, and some synthetic ones may mimic natural fluorescence. Moreover, treatments like heat treatment can affect a ruby's fluorescent properties.

*Comment: I wouldn't personally use this method to verify the authenticity of any single ruby for sale; instead, I would use it to confirm the authenticity of a large number of rubies that you have purchased in a lot (if all the rubies are told to be from the same mine or origin). Use this method as a complement to the following ones!

Gas bubbles are one of the most recognizable indicators of synthetic ruby, and they are directly linked to the way man-made crystals are produced. In processes such as the Verneuil or flame-fusion method, finely powdered aluminum oxide mixed with trace coloring agents is melted in a high-temperature flame and allowed to crystallize layer by layer. During this rapid crystallization, tiny pockets of gas can become trapped within the growing boule. These trapped pockets solidify as bubbles, preserved within the finished crystal.

When viewed under a microscope or through a jeweler’s loupe, these bubbles usually present as perfectly round or spherical inclusions. Their uniformity is striking: they may appear as single isolated spheres, or as small groups scattered throughout the stone. Their size can vary, but what sets them apart is their regular, bubble-like shape, which is very different from the irregular inclusions seen in natural ruby.

By contrast, inclusions in natural rubies tend to be irregular and varied, reflecting the complex geological conditions of their formation. These can include rutile silk in fine intersecting patterns, elongated mineral crystals, or angular growth features and color zoning. None of these resemble the smooth, round geometry of a gas bubble.

For gemologists, the presence of bubbles is therefore a diagnostic feature. While not every synthetic ruby will display them clearly, their appearance under magnification is often enough to separate a flame-fusion stone from a natural ruby. This distinction is critical, since bubbles are not simply imperfections but a fingerprint of artificial growth, one that no natural geological process would produce inside corundum.

When buying or acquiring a ruby that is both vivid in color and loupe clean, an accompanying certificate from a reputable gemological laboratory is absolutely critical (I wouldn't even look at the stone if none is provided. It's a massive red flag!). In the international gemstone market, certification is the standard safeguard for high-value stones, confirming authenticity, treatment status, and origin where determinable. A report from a respected laboratory not only provides assurance of the ruby’s natural identity but also documents its characteristics in a manner recognized by professionals worldwide. Certificates issued by institutions such as Gübelin, SSEF, GRS, GIA, ICA, Bellerophon, or Tokyo Gem Laboratory are considered benchmarks of credibility.

The financial stakes reinforce this necessity. Fine rubies can command prices of many thousands of dollars per carat, and in some cases far more for stones of exceptional size and provenance. In this context, the cost of a laboratory report, typically a few hundred dollars, is insignificant compared to the value of the gem. For serious buyers and sellers alike, the certificate functions as a form of insurance, protecting both parties by substantiating the stone’s worth and eliminating ambiguity.

A transaction involving a top-grade ruby without certification should be treated with extreme caution. The absence of a report raises legitimate concerns about the stone’s origin, treatment history, or even authenticity. While smaller commercial stones are often traded without certificates, this practice is not acceptable for high-quality rubies, especially those marketed as unheated or from prestigious sources such as Mogok or Mozambique.

For those unfamiliar with gemstones, distinguishing between ruby, red spinel, and red garnet can be very challenging. This confusion is not limited to beginners though. Even experienced traders and gem dealers have historically mistaken one for the other. In fact, for centuries red spinels were thought to be rubies, and one of the most famous examples is the Black Prince’s Ruby in the British Crown Jewels, which is in reality a fine red spinel.

To begin separating these stones, it is important to focus on two key aspects: color and inclusions.

Color

Ruby: Typically exhibits a rich and saturated red, often with a slight purplish or pinkish modifier. The best rubies combine depth of tone with vibrancy, appearing both intense and bright.

Red Garnet: Usually lighter in appearance and may display a purplish or brownish undertone. Some garnets can appear wine red or brick red, lacking the vividness of ruby.

Red Spinel: Often shows a lighter and brighter red than ruby, sometimes with a pinkish or orange tint. Fine spinels can rival rubies in beauty, but their hue tends to be slightly more delicate.

Inclusions

Ruby: Almost always contains small inclusions, which can include rutile silk, mineral crystals, or growth zoning. These features are part of the natural fingerprint of corundum and help distinguish ruby from its lookalikes.

Red Garnet: May have fewer inclusions, but when present, they differ in character from those in ruby. Some garnets display needle-like inclusions or crystal patterns unique to their species, which can aid identification.

Red Spinel: Typically has fewer inclusions than ruby, and when present, they are often octahedral crystals or wispy patterns distinct from the silk seen in ruby. High-quality spinel can be very clean under magnification.

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Although these guidelines are helpful, color and inclusions alone may not always provide a conclusive answer, especially to the untrained eye. Proper identification often requires gemological testing, such as refractive index, specific gravity, or spectroscopy, since each of these stones has unique measurable properties.