Obsidian vs Onyx

Obsidian vs Onyx

You’re at the right place if you want to know the key differences between onyx and obsidian gemstones. Keep scrolling to learn more!

Onyx Vs Obsidian

In this guide, we’ll be exploring everything you need to know about onyx and obsidian gemstones along with answering frequently asked questions including:

  • Is obsidian a rock?
  • Is there any difference between black obsidian and black onyx stones?
  • Which of these two black gemstones is best suited for everyday wear?

Origin – Onyx Vs Obsidian


Onyx stones are part of the chalcedony rock family – KAL-SID-NEE. Chalcedony is the same variety as smoky quartz and rose quartz although it’s a type of microcrystalline quartz. As you know, there are different types of quartz. However, this particular one has finer mineral crystals.

Whether or not onyx is an agate which is typically a layered chalcedony is still debatable. Scientists don’t agree with this.

Onyx is a Greek word that means claw. According to Greek mythology, cupid clipped its fingernails while Venus was sleeping and the result was onyx. Early cultures and artisans have been incorporating onyx gemstones in jewelry pieces since time immemorial. It’s debut in 1961 saw it heading the start the Victorian era.

Onyx was mainly used on jewelry pieces worn during mourning and at funerals. The symbolism came to light when Queen Victoria wore an onyx jewelry piece to represent sadness when Price Albert passed on.

Black onyx is mostly used in jewelry pieces like brooches and cameos. Onyx stones were carved and not faceted. Currently, onyx still bears the representation of something mournful and dark coupled with mysticism. You can find onyx stones in different places including Brazil, Madagascar, Uruguay and Canada.


Most people tend to believe tat obsidian stones are smooth, black rocks. They couldn’t be more wrong! Obsidian is one of the most common forms of glass in all its natural glory. It’s usually formed in volcanic lava.

Obsidian is made when volcanic lava cools rapidly with minimal crystal growth. It’s produced from felsic lava containing lighter elements like sodium, potassium, aluminium, oxygen, silicon and sodium. It’s known as obsidian stone as it comes from molten lava.

Just like onyx, obsidian has also been on the market for the longest time. According to history, ancient cultures used obsidian stones like their modern civilization counterparts.

The Mayans were known to use obsidian glass owing to its high value. Plus, it was equally beautiful and abundant in the area. In Mexico, it was referred to as Itzli which translates to god of stone. The Native Americans, Mexicans and Mayans used black obsidian stones to make knives, spearheads and other different weapons.

At that time, jagged obsidian blades were the sharpest of steels. Currently, most people use obsidian stones to make jewelry pieces, decoration carvings and medical instruments. Obsidian is mostly found in areas with volcanic activities.

You can find obsidian stones in active volcanic areas as well as the inactive zones all over the world. However, high-quality obsidian stones are mainly found in the United States, Italy and Iceland. The United States of America is the largest producer of a wide variety of obsidian.

Appearance – Onyx Vs Obsidian


Most people assume that onyx stones are black. However, that is not entirely true because its white and black banded. There are many different varieties with yellow, red, blue and brown banded layers. The most popular variety is the green onyx that is always mistaken for jade or emerald.

Optical Treatments

For the most part, onyx stones are dyed or treated to give them a solid black hue. Another misconception about solid black onyx gemstones is that they’re all treated. The dyes and treatments don’t fade and neither do they decrease the value of the stone. However, extreme heat tends to discolor onyx stones.

Synthetics and Imitations

Just like other gemstones, there are also imitations of onyx owing to material resemblance. Some of the most common onyx simulants include black spinel, synthetic onyx, augite, banded calcite and glass. Synthetic onyx is a combination of different variations of natural gemstones.

Not only can onyx be sold under false names but also misrepresented. Some dealers pass off onyx stones as black tourmaline, black diamond or black spinel.

Some of the most common misleading trade names include onyx marble, limestone onyx and Mexican onyx. It’s not authentic onyx but calcite.


There are different varieties of obsidian stones including:

  • Apache Tears
  • Mahogany obsidian
  • Rainbow obsidian
  • Plesk obsidian
  • Snowflake obsidian

Obsidian glass displays two different types of phenomena associated with gemstones – iridescence and chatoyancy. The latter is the typical cat’s eye effect which is quite common in banded varieties.


High heat can alter obsidian stones with small inclusions. Other obsidian varieties have different inclusions. Iridescence, on the other hand, usually comes from inclusions of specific varieties. To clean obsidian jewelry pieces, use a soft lint-free piece of cloth as opposed to an ultrasonic steam cleaner.

Optical Treatments

Obsidian is not subjected to any kind of treatment because it has a rich body color. Plus, the cost of treatment can surpass the value of the gemstone.

Synthetics and Imitations

You’ll not come across obsidian imitations and lab created obsidian. Glass is used for gemstone imitation and not the imitations with the exception of different glass colors passed off as atypical obsidian. Interestingly, obsidian can pass off as onyx.

Most retailers pass of obsidian stones as onyx since the latter is more desirable.

Price and Value – Onyx Vs Obsidian


Onyx is relatively cheap and of lower value since it’s neither a precious nor a semi-precious gemstone.  The price of onyx stone ranges from $10 to $100 per carat depending on the retailer and quality. For the most part, onyx ring settings are more expensive that the stone itself. This means that repairing or replacing a damaged onyx gemstone is cheaper.

Gemstones with relatively low hardness ratings should be reasonably priced. Onyx engagement rings also fall on the lower side of the pricing spectrum owing to the affordability and abundance of the stone. It would be best to go for onyx as the center stone if you want value for money.

Onyx wedding and engagement rings are quite are in-stores. However, you can easily find them online. An onyx engagement ring can hold up decently even when worn daily. The stone rates at 7 on Mohs hardness scale. This typically means that they have a pretty decent scratch resistance level to dust and dirt in the air.

Other gemstones with the same hardness level include peridot, tanzanite and zircon. Onyx holds up better than other gemstones on the same spectrum since it has no cleavage planes. However, Mohs scale of hardness only measures Scratchability and not durability.

mohs hardness scale


Obsidian stones are not valuable or expensive since they’re in abundance and other obsidian varieties are no exception. The resale value of glass is relatively low and it’s also not as valuable.

However, obsidian sculptures and carvings can be a bit expensive. The prices vary depending on the size of the sculpture, labor and other intricacies. Most people prefer exploring other gemstone options when it comes to engagement rings and it’s for a good reason. One of the most common reasons is because obsidian is not best suited for everyday wear.

Obsidian glass rates at 6 on Mohs hardness scale which makes it more susceptible to damage especially from dust.

Final Thoughts – Onyx Vs Obsidian

Onyx comes highly recommended if you’re choosing between an onyx and obsidian engagement rings. Here’s why:

  • Onyx is best suited for everyday wear.
  • Onyx is more affordable.
  • Onyx is a viable alternative to black diamonds.
  • Onyx is faceted while most obsidian jewelry pieces are carved or en cabochon.
  • Onyx has a higher scratch resistance level as it rates at 7 while obsidian rates at 6 on Mohs hardness scale.

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