Onyx, a captivating gemstone often associated with its striking black variety, is much more than meets the eye. This comprehensive guide delves into the world of onyx, exploring its composition, colors, durability, and value, offering insights for both jewelry enthusiasts and those simply curious about this fascinating stone.
What Does Onyx Look Like?
While many picture onyx as a solid jet-black stone, often with parallel white bands, its appearance is diverse. Onyx is a variety of chalcedony, a silicate mineral primarily composed of calcite. While black onyx is incredibly popular, it also presents itself in shades of brown, red, and white. Brown and white onyx is often referred to as sardonyx, while the red and white variation is known as carnelian onyx.
The characteristic feature of all onyx types is their layered structure, with lighter bands typically overlying darker ones. This property has historically made onyx a favored material for carving, particularly for cameos, where a raised design is created by removing the darker layer to expose the lighter layer beneath.
What is Onyx Made Of?
Onyx forms naturally within caves and bedrock openings around the globe from calcite, the same mineral found in limestone, travertine, and marble. The process begins with dripping spring or groundwater rich in dissolved calcite from stalactites and stalagmites. As the water evaporates, it leaves behind trace minerals and calcium carbonate, resulting in the stone’s characteristic banded appearance.
These bands are created by alternating layers of silica minerals, quartz, and morganite, which deposit parallel to each other. This formation process is similar to that of agate, which often leads to confusion between the two. However, the key difference lies in the layering: agate exhibits curved, rather than parallel, bands.
Where Does Onyx Come From?
Onyx is found in many locations worldwide. Some of the major sources include:
- Afghanistan
- Australia
- Argentina
- Brazil
- Botswana
- Canada
- China
- Czech Republic
- France
- Germany
- India
- Madagascar
- Mexico
- Pakistan
- Russia
- Serbia
- The UK
- Uruguay
- Yemen
Onyx is also mined in certain regions of the United States.
Is Onyx Durable?
Onyx has a Mohs hardness rating of 6.5 to 7. This means it is moderately durable, suitable for jewelry that is not subjected to excessive wear and tear.
Here’s a summary of onyx’s key properties:
| Chemical Formula: | SiO2 |
|---|---|
| Density: | 2.58-2.65 |
| Refractive Index: | 1.530-1.540 |
| Lustre: | Vitreous |
What is Black Onyx?
Black onyx is arguably the most recognized and sought-after variety of onyx. It features a black base overlaid with parallel white bands. As mentioned earlier, it can be confused with black agate; however, the parallel banding is the key distinguishing feature. Throughout history, black onyx has been associated with various symbolic meanings, ranging from discord to protection and grounding, especially within Feng Shui practices.
What Does Raw Black Onyx Look Like?
Raw black onyx is not always uniformly black. In its natural state, it can appear brownish-gray or even dark green. The deep, opaque black color that it’s known for is due to the density of the color within the stone. Because naturally occurring deep black onyx is rare, many jewelers use dyed chalcedony to achieve the desired jet-black color.
Sourcing raw black onyx can be challenging as it’s often easier to mine red or brown onyx and then dye it black. Therefore, caution is advised when purchasing onyx.
How to Identify Black Onyx?
Identifying genuine black onyx requires some knowledge and careful observation. Here are a few methods to help differentiate between real and dyed onyx:
- The Heat Test: Real onyx will feel cool to the touch, even in warm conditions.
- The Scratch Test: Using a material with a Mohs hardness of less than 6 (such as a copper coin or a fingernail), gently scratch the non-decorative side of the stone. Real onyx should blemish, but not scratch.
- The Acid Test: Onyx contains quartz, which is resistant to many acids. A drop of muriatic or oxalic acid on real onyx should not cause a reaction. If fizzing or bubbles occur, the stone is likely not real onyx.
If you are unsure, consulting a qualified gemologist is always a good idea. It’s also important to be aware that some jewelers may use dyed black agate, black spinel, or jade, mislabeling them as onyx. Ensuring you trust the supplier’s knowledge and ethical sourcing practices is critical.
Does Black Onyx Scratch Easily?
Under normal circumstances, black onyx does not scratch easily. However, it can chip or crack if subjected to significant impact. While not the hardest gemstone, its 6.5-7 Mohs rating makes it reasonably durable for jewelry.
Can Black Onyx Go in Water?
Yes, black onyx can safely be exposed to water, making it suitable for everyday wear, even in the shower or during cleaning.
Its tolerance allows for cleaning with warm water, mild soap, and a soft brush. Ultrasonic or mechanical cleaning equipment should be avoided. After cleaning, simply allow the onyx to air dry.
Is Black Onyx Expensive?
Genuine, naturally occurring black onyx can be quite expensive due to its rarity and high demand. If a gemologist has certified a stone as real black onyx, it can be quite valuable.
Dyed onyx offers a more affordable alternative. It can add a unique look to jewelry designs without the expense of sourcing rarer and pricier stones like black diamonds.
What is Black Onyx Good For?
In the jewelry industry, black onyx is often used to create smooth cabochon stones for rings and pendants. Its glossy luster complements silver or gold settings beautifully. Its relative affordability makes it a popular choice for both jewelers and consumers.
In conclusion, onyx is a versatile and fascinating gemstone with a rich history and a wide range of uses. Whether you’re drawn to its classic black variety or its more colorful variations, onyx offers a unique and beautiful addition to any jewelry collection.
