7 Easy Ways To Tell Onyx Is Real

In the captivating world of gemstones, onyx, with its deep, dark allure and unique patterns, holds a coveted spot. Revered by many cultures throughout history for its distinct beauty and perceived mystical properties, it continues to be a favourite choice in jewellery and decorative pieces. However, the gemstone market is not free of counterfeit products, and faux onyx is no exception. This unfortunate reality makes it challenging for the untrained eye to distinguish genuine onyx from cleverly disguised imposters.

But worry not, as this daunting task is more manageable than it seems. Armed with the right knowledge, anyone can develop a keen eye for spotting the real deal.

This blog post aims to provide you with practical and reliable ways to test if onyx is real, ensuring that you never fall prey to the world of gemstone fakes. From understanding its inherent physical properties to conducting simple at-home tests, we will guide you on your journey towards becoming an onyx connoisseur. Buckle up, and let’s delve into the mesmerizing world of onyx authenticity!

What Is Onyx?

Onyx is a type of chalcedony, which is a sort of cryptocrystalline or microcrystalline quartz. It’s formed from the deposition of silica within gas cavities in lava, which results in a layered structure and a variety of beautiful colours and patterns.

Onyx, in its most accepted definition, is characterized by parallel layers of black and white. However, the term is often used to describe any chalcedony with parallel banding, and that can include a wide range of colours.

One unique feature of onyx is its waxy lustre when polished. This property makes it an excellent material for making jewellery, carvings, and other decorative items. Onyx has been used for carving since ancient times. Roman soldiers, for example, carried amulets made of onyx engraved with Mars, the god of war, hoping it would make them brave.

In metaphysical belief systems, onyx is often thought to provide protection and strength. It is also believed to help with stress, grief, and negative thinking, although these properties are not scientifically proven.

In sum, onyx is a versatile and beautiful gemstone with a rich history and a wide range of uses in the modern world. Its unique appearance, combined with its long cultural history, make it a fascinating subject of study for gem enthusiasts and a highly sought-after material for artisans and consumers alike.

What Does Real Onyx Look Like?

Real onyx is a gemstone with a unique and recognizable appearance. Here’s how to identify it:

Colour: Traditionally, onyx is known for its striking black and white banding, although it can come in a variety of other colours. The bands, which are parallel, may be just one colour or alternating, typically in shades of black, white, or grey. Onyx is often dyed to enhance its colour, especially to achieve a solid black.

Pattern: Onyx is recognized for its consistent, straight bands. Unlike agate (another variety of chalcedony), which has curved or concentric bands, onyx’s banding is parallel and layered, often in a more regular and predictable pattern.

Texture: Polished onyx has a smooth texture and a waxy lustre. It’s somewhat cool to the touch, similar to most other types of stone.

Translucency: While many types of chalcedony are translucent to semi-transparent, onyx is typically opaque, which means you can’t see through it. This is especially true for darker stones.

Hardness: Onyx has a tough surface of 6.5 to 7 on the Mohs scale, which shows it’s not soft, but not as hard as, say, quartz or diamond.

Keep in mind that onyx is often imitated by other materials, including glass and plastic, and it’s also commonly treated to enhance its appearance. If you’re buying onyx, it’s a good idea to purchase from a reputable dealer who can attest to the stone’s authenticity. If you have any doubts about a particular piece, a qualified gemmologist should be able to help.

Easy Was To Tell That Onyx Is Real

It is Translucent

Onyx, particularly black onyx, is usually opaque, which means it doesn’t allow light to pass through. However, some types of onyx may show a degree of translucency when held up to a light source, especially if the stone is thin or lightly colored. This quality can be one of the various characteristics to help determine its authenticity. Here’s how to tell if onyx is real:

Examine the Colour and Pattern: Authentic onyx has parallel bands, often black and white or in shades of gray. The bands should be consistent and straight, not irregular or curvy. Also, if the onyx is solid black, it might be dyed – a common practice to enhance the stone’s appearance.

Feel the Temperature: Like other gemstones, onyx will feel cool to the touch, even if it’s been in a warm room. This characteristic is due to its high thermal conductivity. Synthetic materials like plastic or glass tend to warm up more quickly and retain heat longer than natural stones.

Check the Hardness: Onyx falls at 6.5 to 7 on the Mohs hardness grade. This shows it’s a fairly hard stone and will be able to scratch glass or a steel blade, but not as hard as a diamond, ruby, or sapphire.

Inspect the Lustre: Authentic onyx has a waxy luster when polished, not a glassy one. This means it should have a soft, glowing shine rather than a sharp, mirror-like reflection.

Perform a Light Test: While black onyx is usually opaque, lighter-colored onyx might be somewhat translucent. By shining a light through the stone, you can sometimes spot irregularities or structures within it that might not be visible otherwise. A completely uniform appearance may suggest a synthetic material.

Consult a Professional: If you’re still unsure about your onyx’s authenticity, it’s best to consult a gemmologist or a reputable jeweller. They will have the tools and knowledge to confirm whether your stone is real or not.

Remember, these are just general guidelines. It’s always best to consult with an expert if you’re planning on purchasing onyx, especially if it’s a significant investment.


The weight or specific gravity of onyx can be another important clue when trying to determine its authenticity. The specific gravity of a gemstone is the ratio of its density compared to an equivalent volume of water. The specific gravity of onyx is approximately 2.6 g/cm3. This is higher than the specific gravity of most plastics and lower than the specific gravity of most types of glass or other common imitation materials.

To get a feel for this at home without any specialized equipment, you can compare the weight of the suspected onyx stone in your hand to a similar-sized stone of known composition, like quartz. Quartz has a higher specific gravity (about 2.65 g/cm3), so if your onyx stone feels significantly lighter than a similar volume of quartz, it might not be genuine.

For a more precise measurement, you would need a hydrostatic weighing scale. This tool measures the weight of the stone in air and in water and uses the difference to calculate the stone’s specific gravity. A significant deviation from the typical range for onyx would suggest that the stone is not genuine.

However, weight alone can’t definitively determine the authenticity of an onyx stone, as other materials could have a similar specific gravity. It’s just one clue among many. Other factors, such as the stone’s color, pattern, hardness, temperature to the touch, lustre, and the way it interacts with light, should also be considered.

It’s always advisable to consult with a gemmologist or a reputable jeweller if you’re unsure. They will have the expertise and tools to confirm whether a stone is real onyx.

Hardness Of The Stone

The hardness of a stone is a measure of its resistance to being scratched. This property can be particularly useful in identifying gemstones, including onyx. The hardness of onyx is 6.5 to 7 on the Mohs scale, which is a system used to classify minerals by their hardness. For reference, a fingernail has a hardness of about 2.5, a steel file about 6.5, and a diamond, the hardest natural substance, is rated 10.

So, how can you use this information to determine if onyx is real?

Here’s a simple test you can do at home. Since a steel file has a similar hardness to onyx, it should not be able to scratch a real onyx stone. Try scratching an inconspicuous part of the stone with a steel file. If it leaves a mark, the stone is softer than onyx and likely a fake. Remember to be very careful while doing this to avoid any potential damage to the stone.

Another test involves glass, which has a hardness of about 5.5 on the Mohs scale. A genuine onyx should be able to scratch a piece of glass without getting scratched itself.

Keep in mind, these tests may not be 100% conclusive since there are other materials with similar hardness. They should be used as part of a suite of tests, alongside examining colour, patterns, weight, and other properties. Also, these tests can potentially damage the stone, so they should be performed cautiously, ideally on a part of the stone that is not visible when it’s set in jewellery.

For a definitive identification, it is always advisable to have the stone tested by a certified gemmologist. They will be able to conduct a thorough examination using professional tools, such as a refractometer, a dichroscope, or a microscope, and their expertise in gemmology.

Real Onyx Is Expensive

The price of onyx, like all gemstones, is influenced by several factors including its quality, size, treatment, supply, and demand. While onyx is not the most expensive gemstone on the market, genuine, high-quality onyx can indeed command a higher price.

Here are some reasons why real onyx may be relatively expensive:

Quality: High-quality onyx is determined by its colour, clarity, and lustre. Onyx with clear, distinct banding or a deep, rich black colour is more desirable and thus more expensive.

Size: Large pieces of onyx are rarer and therefore cost more. This is particularly true for onyx used in statement pieces like cocktail rings or pendant necklaces, where a large, single piece of the gemstone is showcased.

Treatment: Many onyx stones on the market are treated to enhance their colour and clarity. Untreated, natural onyx is rarer and typically more expensive.

Craftsmanship: Onyx that has been expertly cut and polished will be more expensive than stones that have not been as skilfully prepared. In addition, onyx used in fine jewellery where the craftsmanship and design are exceptional may command a higher price.

Supply and Demand: The cost of onyx can also fluctuate based on supply and demand. If a particular type of onyx becomes trendy or there’s a dip in the supply, the price could rise.

That said, it’s important to note that while genuine onyx can be relatively expensive compared to imitation stones or glass, it’s generally more affordable than many other gemstones like diamond, ruby, or emerald.

Additionally, many factors can impact the price of onyx jewellery, including the type and quality of the metal used, the reputation of the designer or brand, and whether the piece is new or antique. Therefore, if you’re seeing a piece of onyx jewellery or a loose onyx stone that seems unusually cheap, it’s a good idea to question its authenticity. As always, buying from reputable dealers and requesting certification where possible is the best way to ensure that you’re getting genuine onyx.

Texture of the Onyx

The texture of onyx can indeed provide valuable clues about its authenticity. Here’s what to look for:

Smoothness: Genuine onyx, when polished, has a very smooth surface. If you run your finger over it, it should feel slick, without any bumps or rough patches.

Luster: Real onyx has a waxy luster. This means it should have a soft, glowing shine rather than a sharp, mirror-like reflection. If the stone has a glass-like luster, it could be glass or synthetic material.

Temperature: Genuine onyx, like other gemstones, will feel cool to the touch even in a warm room due to its high thermal conductivity. In contrast, plastic or glass will warm up more quickly.

Surface Features: Genuine onyx can have small pits, lines or other natural surface features, while fake onyx (usually plastic or glass) might be perfectly smooth with no such imperfections. However, this isn’t a definitive test, as well-crafted fakes may also include these features to mimic natural onyx, and high-quality natural onyx may be polished to remove such imperfections.

Consistency: If the piece of onyx is banded, the bands should be consistent and parallel. Irregular banding may indicate that the stone isn’t genuine.

As with other tests for authenticity, examining the texture of onyx should be used in conjunction with other methods like checking the colour, hardness, and weight, and performing a light test. Furthermore, while these tips can help you make an initial assessment, a professional gemmologist or reputable jeweller should be consulted for an authoritative identification.

A Breaking test

The “breaking test” or “fracture test” is often used by professionals to determine the authenticity of a stone. It refers to observing the stone’s break or fracture pattern. However, it’s crucial to understand that this test involves potentially damaging or entirely breaking the stone, so it’s generally not recommended for anyone other than a professional gemmologist.

When it comes to onyx, it typically breaks with a conchoidal fracture, similar to what you would see when glass is broken: it’s shell-like with smooth, curved surfaces. A stone that shatters into sharp, angular pieces or shows a granular fracture instead is likely not genuine onyx.

It’s also worth noting that the fracture surface of natural onyx should not appear glassy or shiny. Instead, it should be relatively dull or matte. A glassy breakage is typically indicative of a synthetic material or glass.

While this method can be quite revealing, remember that it is destructive and should only be used as a last resort. Also, it requires knowledge and expertise to correctly interpret the results. If you’re uncertain about the authenticity of your onyx, it’s always best to consult with a certified gemmologist or a reputable jeweller. They can use non-destructive methods and advanced tools to accurately determine whether your stone is real onyx.

Heat Test

A heat test is a method that can sometimes be used to determine the authenticity of a gemstone. However, it’s important to note that this method is not recommended for amateurs or anyone untrained in gemmology, as it can permanently damage the stone, and the results can be difficult to interpret without expert knowledge.

Genuine onyx is relatively heat resistant due to its mineral composition. That is, it won’t easily melt or warp under high temperatures as some artificial materials might. However, onyx can still be affected by sudden temperature changes or extreme heat.

For example, exposing onyx to heat might cause it to crack or change colour, and any treatments (like dyeing) could be altered or destroyed. Furthermore, other natural gemstones and some synthetic materials can also be heat-resistant, so a heat test alone won’t definitively identify onyx.

A professional gemmologist could potentially use heat testing in combination with other tests to identify a stone, but again, it’s not a method you should try to carry out at home.

If you suspect your onyx might be fake, the best course of action is to consult with a reputable jeweller or gemmologist. They can perform a variety of non-destructive tests to accurately identify the stone and can advise you on the best way to care for it.


Mohs Hardness Scale Explained

Scroll to Top