Onyx vs Obsidian: Key Differences (Which is Better For You?)

Last Updated on December 28, 2022 by Juli "Jewels" Church

Having a tough time choosing between onyx or obsidian jewelry?

Perfect, you're in the right place! 

In this Learning Guide, I'll answer the top questions asked about both of these popular black gemstones like:

onyx vs obsidian
  • Which is Better for Everyday Wear?
  • What Are The Differences Between Black Onyx and Black Obsidian?
  • Is Obsidian A Rock?

Onyx vs Obsidian: Origin


Onyx gemstones come from the rock family of chalcedony (KAL-SID-NEE). Chalcedony is a type of microcrystalline quartz. However, it's the same variety you might be familiar with, like rose quartz or smoky quartz. 

This type of quartz has very fine mineral crystals. There's some argument over if onyx is an agate, another layered chalcedony. But scientists have settled against this.

The name “onyx” is derived from the Greek word for “claw”. Greek mythology tells us that while Venus was sleeping, Cupid clipped her fingernails and the clippings were onyx. 

Artisans and early cultures have been using onyx in jewelry for thousands of years. Its debut headed off the start of the Victorian era in 1861. 

It was used mostly for jewelry worn at funerals or in times of mourning. This symbolism occurred after Queen Victoria donned a piece of onyx jewelry to represent her sadness about Prince Albert’s passing. 

Most of the use of black onyx in jewelry had been for cameos and brooches. Onyx was carved rather than faceted. 

Today, onyx still means something dark and mournful, with some mysticism thrown in. You can find an onyx stone in places like Brazil, Canada, Uruguay, and Madagascar. 


A lot of people think obsidian is a smooth, black rock. Instead, it’s the most common form of natural glass. It's formed in volcanic lava . Obsidian is made when felsic lava erupts.

Because it comes from molten lava, they still call it obsidian stone. Like onyx, people have been working with obsidian for years. History shows us that ancient civilizations used it as well as modern civilizations. 

The Mayans were notably famous for using obsidian glass. They deemed it high value because of its beauty and abundance in the area. The Mexicans called the stone Itzli, meaning the “god of stone”. 

The Mayans, Mexicans, and Native Americans all used black obsidian stone to make spear heads, knives, and other weapons. A jagged obsidian blade was sharper than any steel they had. 

Presently, obsidian is used to make jewelry, carvings for decorations, and some medical instruments. 

You can find obsidian in areas of volcanic activity. Obsidian is mined from inactive volcanic areas, but can be found in active areas too. It’s found all over the world. The biggest places known for obsidian are Iceland, Italy, and the United States. The US is a large producer of different varieties of obsidian. 

Onyx vs Obsidian: Appearance


If you’re like me, you might have assumed that onyx stones are black. I believed this so much that I named my black cat after it. Low and behold, it’s not entirely true. It’s black and white banded.

Other varieties of onyx can have red, yellow, brown, and blue banded layers. Green onyx is a popular variety that's often mistaken for emerald or jade.

Optical Treatments

Onyx is commonly treated or dyed to give a solid black color. It should be assumed if your onyx is solid black, it has been treated. The treatments and dyes don’t decrease the value and they don’t tend to fade either. You should keep onyx away from extreme heat because that can discolor it. 

Synthetic Onyx and Onyx Imitations

Other gem materials look like onyx, so you should beware of imitations. The most common onyx simulants are banded calcite, black spinel, glass, augite, and synthetic onyx. Synthetic onyx is made by combining other natural gemstones. 

Onyx can also be misrepresented as other gemstones or have false names. Some dealers may pass black onyx off as black spinel, black diamond, or black tourmaline.

False trade names of onyx are seen as "Mexican onyx", "limestone onyx", and "onyx marble". It's calcite, not real onyx. 


Most people assume black obsidian is the only obsidian. There are a variety of obsidian types:

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

Obsidian glass can display two types of gemstone phenomena: chatoyancy and iridescence. Chatoyancy is the “cat’s eye” effect. Banded varieties create this effect. 

Obsidian can have small inclusions that can be altered by high heat. Other varieties of obsidian have different types of inclusions. The iridescence comes from the inclusions of certain varieties. 

You shouldn’t use any kind of ultrasonic or steam cleaner to clean obsidian jewelry. A lint-free cloth is the best option. 

Optical Treatments

Obsidian isn’t treated because the color is already throughout it. The cost of applying a treatment would exceed the value of the obsidian itself. 

Synthetic Obsidian and Obsidian Imitations

You shouldn’t come across any lab grown obsidian or obsidian imitations. Glass is normally used for gem imitations, not imitations themselves. The exception to this is other colors of glass being passed off as rare obsidian. 

Interestingly enough, obsidian is sometimes passed and sold off as onyx because onyx is more desirable. 

Onyx vs Obsidian: Price & Value


Onyx isn’t considered a precious or semi-precious gemstone, so it’s not very expensive, or valuable. They can cost $10 per carat to $100 per carat, depending on quality and retailer. 

Most of the time, onyx ring settings cost more than the actual stone itself.

That’s good news because if you do damage the stone at all, it’s not too expensive. That’s better for gemstones with lower hardness ratings to be less expensive. 

The monetary value isn’t high with onyx engagement rings because of its abundance and affordability. You can get your money’s worth if you still opt for onyx as your center stone. 

Onyx engagement and wedding rings aren’t common in-stores. You’ll have better luck finding it online. Onyx engagement rings hold up pretty decently for frequent wear. 

They rate a 7 on the Mohs scale of hardness. This means their scratch resistance to dust is pretty decent. Other stones on this spectrum would include zircon, tanzanite, and peridot. 


It doesn’t have cleavage planes, so it’ll hold up better than other gemstones with the same Mohs rating. The hardness scale is just scratchability, not durability. Every day dust  and dirt are the biggest scratch threats to gemstones. 

Onyx engagement rings are often set in yellow gold. The two colors contrast really well and it makes the onyx center stone stand out more. Many choose small white diamonds as melee stones for their ring settings. 


Obsidian isn’t expensive or valuable because of how abundant the material is all over the world. That also goes for the different varieties of obsidian. Glass is not valuable at all, nor does it have good resale value. 

The exception to this would be obsidian carvings and sculptures. For the labor, intricacies, and size of an obsidian sculpture, prices can vary. Those factors will cost more than the obsidian glass. 

People don’t usually choose obsidian engagement rings for a number of reasons. The biggest reason is because it doesn’t hold up for everyday wear. 

Obsidian glass hits a 6 on the Moh scale. Dust is a 7, so obsidian will likely be damaged in daily wear. This can be avoided by frequent cleaning and care, but a lot of people don’t have the time or patience. 

You’ll have a harder time finding obsidian engagement rings vs onyx engagement rings. 

If you do, they're more like to be set in steel or sterling silver at most. An obsidian necklace is more popular than an obsidian engagement ring

When people intend to use obsidian as a center stone, they’re looking for the black variety. There are other black gemstones that hold up better daily than obsidian glass, so they’re often chosen over it. 

Most people don’t want a black glass ring if they can opt for a different black stone that is still affordable, like onyx. 

Bottom Line: Onyx vs Obsidian

If you’re trying to choose between an onyx engagement ring or an obsidian engagement ring, I recommend you go with onyx.

Here’s are some of the reasons why: 

  • Onyx has better scratch resistance sitting at a 7-7.5 on the Mohs scale
  • Onyx is better for wearability, obsidian is easily damaged
  • Onyx is often faceted, most obsidian jewelry is en cabochon or carved
  • Onyx is used as an alternative to buying black diamonds
  • Onyx is affordable and able to be set in precious metal for engagement rings

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