how to tell if onyx is real need to know before deciding

How to tell if onyx is real

Onyx, a strikingly beautiful and versatile gemstone, has been cherished for centuries for its deep, rich colors and unique banding patterns. However, with the rise of synthetic and imitation stones, it has become increasingly important to know how to distinguish genuine onyx from its counterfeit counterparts. This guide will provide you with detailed information on how to tell if onyx is real, ensuring that you make informed decisions when purchasing or evaluating this exquisite gemstone. how to tell if onyx is real.

how to tell if onyx is real need to know before deciding

What is Onyx?

Onyx is a variety of chalcedony, a mineral in the quartz family. It is characterized by its parallel banding, which can come in a variety of colors, although black and white are the most common. The bands in onyx are typically straight and parallel, which distinguishes it from agate, another form of chalcedony with curved or chaotic banding.

Physical Properties of Onyx

Color and Banding

The most distinctive feature of onyx is its banding. Genuine onyx typically has straight, parallel bands that can be black, white, brown, red, or green. The bands are usually of contrasting colors, creating a striking visual effect.

Hardness and Durability

Onyx has a hardness of 6.5 to 7 on the Mohs scale, making it relatively durable but still susceptible to scratching and chipping. This hardness level is a key factor in distinguishing real onyx from softer imitation stones.

Luster and Transparency

Onyx has a vitreous (glassy) luster and is usually opaque, although some specimens can be slightly translucent. The luster and transparency can help in identifying genuine onyx, as imitations often lack the same quality. how to tell if onyx is real.

how to tell if onyx is real.

Methods to Identify Real Onyx

Visual Inspection

Examine the Banding

One of the first steps in identifying real onyx is to closely examine the banding. Genuine onyx will have straight, parallel bands of contrasting colors. If the bands are wavy, chaotic, or too perfect, it may be an indication of a synthetic or imitation stone.

Check the Color

While black and white are the most common colors, onyx can also come in shades of brown, red, and green. Be wary of stones with overly vibrant or unnatural colors, as these may be dyed or synthetic. how to tell if onyx is real.

Hardness Test

Onyx has a hardness of 6.5 to 7 on the Mohs scale. You can perform a simple scratch test using a material of known hardness, such as a steel nail (hardness 5.5) or a piece of quartz (hardness 7). If the onyx scratches the steel but is scratched by the quartz, it is likely genuine.

Heat Test

Genuine onyx is a natural stone and will not be affected by heat. You can perform a heat test by holding the stone over a flame for a few seconds. If the stone remains unchanged, it is likely real. However, if it shows signs of melting, discoloration, or emits a chemical smell, it is probably an imitation.

Specific Gravity Test

Onyx has a specific gravity of 2.55 to 2.70. You can measure the specific gravity using a hydrostatic balance or a simple water displacement method. This test can help distinguish onyx from lighter or denser imitation stones. how to tell if onyx is real.

Professional Gemological Testing

For a definitive identification, consider having the stone tested by a professional gemologist. They can use advanced techniques such as spectroscopy, X-ray diffraction, and electron microprobe analysis to determine the stone’s composition and authenticity.

Common Onyx Imitations

Dyed Agate

Agate, another form of chalcedony, is often dyed to mimic the appearance of onyx. Dyed agate can be identified by examining the color distribution and banding. The dye may not penetrate evenly, resulting in uneven or blotchy colors. how to tell if onyx is real.


Glass is a common imitation material for onyx. It can be identified by its lower hardness (around 5.5 on the Mohs scale) and lack of natural banding. Glass imitations may also have air bubbles or other inclusions not found in natural onyx.


Plastic imitations are usually easy to identify due to their low hardness and lightweight. They may also emit a chemical smell when subjected to the heat test.

Tips for Buying Real Onyx

Buy from Reputable Sources

One of the best ways to ensure you are purchasing genuine onyx is to buy from reputable sources. Established jewelers and gemstone dealers are more likely to provide authentic stones and can offer certification or guarantees of authenticity.

Ask for Certification

When purchasing high-value onyx, ask for a certificate of authenticity from a recognized gemological laboratory. This certificate will provide detailed information about the stone’s properties and confirm its authenticity. how to tell if onyx is real.

Be Wary of Deals That Seem Too Good to Be True

If a deal seems too good to be true, it probably is. Be cautious of sellers offering onyx at significantly lower prices than the market average, as this may indicate an imitation or synthetic stone.

how to tell if onyx is real

Caring for Your Onyx


To clean onyx, use a soft cloth and mild soap with warm water. Avoid using harsh chemicals or ultrasonic cleaners, as these can damage the stone. Gently wipe the stone and dry it thoroughly to maintain its luster. how to tell if onyx is real.


Store onyx separately from other gemstones to prevent scratching. Keep it in a soft pouch or a lined jewelry box. Avoid exposing onyx to extreme temperatures or direct sunlight for prolonged periods, as this can cause fading or damage. how to tell if onyx is real.


Handle onyx with care to avoid chipping or scratching. Remove onyx jewelry before engaging in activities that may cause impact or abrasion, such as sports or heavy manual work.

The Role of Onyx in Modern Design

Onyx in Jewelry

Onyx continues to be a popular choice for jewelry due to its striking appearance and versatility. It is used in various types of jewelry, including rings, necklaces, bracelets, and earrings. Onyx can be set in different metals, such as gold, silver, and platinum, to create both classic and contemporary designs.

Statement Pieces

Onyx is often used to create bold, statement pieces that draw attention. Its deep, rich colors and unique banding make it an excellent choice for eye-catching designs. Large onyx cabochons or faceted stones can be the centerpiece of a stunning piece of jewelry. how to tell if onyx is real.

Everyday Elegance

In addition to statement pieces, onyx is also used in more subtle, everyday jewelry. Smaller onyx stones can add a touch of elegance to simple designs, making them suitable for daily wear. Onyx beads and pendants are popular choices for creating versatile and stylish accessories.


Identifying real onyx requires a combination of visual inspection, physical tests, and professional evaluation. By understanding the unique properties of onyx and being aware of common imitations, you can make informed decisions when purchasing or evaluating this beautiful gemstone. Remember to buy from reputable sources, ask for certification, and care for your onyx properly to ensure it remains a cherished part of your collection for years to come. how to tell if onyx is real.

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