In medieval times, the typical associations that went with the color black were the gloomy themes of negative energy, evil, and death. Hence, it is no surprise that, in that era, most peoples considered black gemstones unsightly and potential harbingers of doom.

While black still maintains its status in the west as the color of sadness, morning, and death, its reach has expanded to several other themes.

Today, with western fashion, wearing the color black can often be the epitome of being a contrarian. Black can represent everything from rebellion to strength, confidence, mystery, and sexiness.


With clothing, black can also be an excellent color for formal outfits, with which they represent seriousness, professionalism, and authority.

Consequently, black gemstones like black sapphire, black spinel, black diamond (, carbonado diamonds), obsidian, and onyx have seen a corresponding uptick in use cases, popularity, and demand.

Black jewelry can be excellent for adding a touch of mystery, sophistication, or elegance to any outfit. Done right, you can create several different eye-catching or intriguing looks with these stones.

If you are in the market for a new black piece, black diamond and onyx are two material types that are sure to pop up the most. Which one is right for you?


Black Diamond

For black stone lovers, black diamonds represent the quintessential black gem. These gemstones are diamonds that sport a natural black color, thanks to inclusions of other darker minerals like graphite or hematite.

Major selling points for the black diamond include the fact that its a diamond. Hence, you get the allure, extreme hardness, and durability while getting gemstones that retail for a fraction of the price of other types of diamonds.

Plus, black diamonds are some of the most striking black stones. These gems often feature deep, eye-catching blacks dues to the opaqueness that results from either natural or synthetic graphitization.


On the other hand, onyxes are a different type of black stone that brings its own distinctive appeal. Onyxes are a type of chalcedony (a microcrystalline variety of quartz) that comes with straight, almost parallel layers of colors.

This unique physical appearance makes this gemstone an instant hit with artists and gem carvers, as they can easily chip off portions of the upper layers to create eye-catching cameos and other art pieces.

The traditional black onyx (also known as Arabian onyx) is an all-black stone or a black stone with white bands. This color combination is a favorite for both people who want the limitless artistic possibilities that it brings and folks who desire an alluring untouched black gem.

Fun Fact

While the traditional color for onyxes is black with white undertones, you can also find rare onyxes with a wide variety of colored bands

Hence, it is no surprise that onyxes are some of the most popular dark stones, maintaining this status across Asia and the Americas for centuries.

Black Diamond vs. Onyx

Black diamond and onyx are two gemstones from considerably dissimilar families that exhibit markedly different physical properties.

However, one major uniting factor between both stones is their color and their popularity. When you shop for black gems, the chances are that most of the popular options available to you will fall into one of these two categories.

Nevertheless, that is where the similarities end. Anyone who is well acquainted with both stones can instantly tell them apart based on their look and feel.

Appearance and Luster

The significant similarity between these gemstones is that they are both black. However, even there, when you take a closer look, you will find that differences abound.

The black color in black diamonds comes from the rock’s inclusions rather than from the original crystallization. Black diamonds often contain many tiny inclusions of darker minerals that give the structure its dark hue.

Consequently, the color grade of a black diamond can vary significantly depending on the size, amount, and distribution of the inclusions. It can range anywhere from faint gray to pitch black.


Most black diamonds available on the market undergo further synthetic graphitization to create the more even black tone of traditional Carbonaro diamonds.

These diamonds pack far less brilliance than their colorless and other colored counterparts. However, in the world of black gems, they rank up there as some of the more shiny stones.

Black diamonds, especially evenly saturated stones, will have significant opaqueness and a distinct metallic luster that gives it an intriguing, mysterious vibe and sets it apart from most other black gemstones. Faceting a black diamond can further enhance this effect to create genuinely eye-catching pieces.

On the other hand, with onyx, you get a gemstone that exudes even less luster than most black diamonds. Black onyxes will absorb most light you throw at them and will leave you staring at its opaque, glassy surface.

However, onyxes with a solid black top layer typically sport a high gloss surface, akin to glazed ceramic, that adds considerable allure to the gem, despite not matching the shine you get with black diamonds.

Plus, thanks to their extra thin color layers, onyxes are extremely porous and can readily be dyed to reinforce their color and add to its good looks.


Most black onyxes on the market today contain dyes that further enhance their black color

The clincher in favor of onyxes is their extreme customizability, thanks to the presence of multiple color layers and their relative softness that makes them easier to cut and carve. If you are interested in cameos and other forms of artistic modifications of your gems, onyx is the clearcut choice.


Black diamonds typically sport deep blacks and attractive metallic shine that makes them the arguably better-looking stone of the two. However, onyxes’ customizability and their distinct glazed ceramic look bring enough allure to win the heart of many potential buyers.

Hardness and Durability

The potential durability of these stones is a significant divider that will considerably influence many shoppers’ buying decisions.

Diamonds are the hardest naturally-occurring substances known to man, and they max out the Mohs hardness scale with a hardness level of 10. On the other hand, onyx is significantly softer, coming in at only a 7-Mohs hardness level.

The implications of these details in real-life usage are considerable.

Diamond jewelry is almost sure to last longer than any onyx piece, as they are far less likely to damage under the same amount of pressure. Diamonds will suffer less when roughly handled, and you can relax more without worrying about denting your piece every time you move.


While black diamonds are some of the hardest stones on earth, due to their unique structure that often features smaller bits fused together, some rocks may contain fractures that can break the gem’s bonds if pressured.

The porosity of onyx also presents another problem with safe handling. Onyxes can easily absorb any solutions you place it in, so you want to avoid the use of most jewelry cleaners as they contain chemicals that can dye or potentially damage the stone.

Furthermore, onyxes often have extra-thin layers of color. Worse still are artificially blackened onyxes often have a top black coating that can be less than a tenth of an inch. With color layers this slim, you can easily damage the look of the stone when polishing it.

Market Value

The flipside to onyx being less hard and more prone to damage than black diamonds is that they are significantly cheaper. Hence, buyers are likely to be comfortable wearing their onyxes as daily wear, and never have to fear losing a fortune if they damage them.

Although all-black onyxes are more valuable than stained and other colored options, compared to all other stones, they are some of the cheaper gems. Depending on quality, you can get black onyxes for anywhere from $1 to $200 per carat.

With black diamonds, prices head towards the other end of the spectrum, with GIA-certified natural black diamonds often retailing for as high as $2000 per carat.

However, if you favor synthetic black diamonds, you can get far less steep prices in the $80 to $200 per carat range.

Both black diamonds and back onyxes can vary significantly in price depending on their natural color, inclusions, smoothness of their surfaces, and porosity. Porous black stones are more likely to suffer from physical or chemical damage and hence are typically cheaper.

Use and Popularity

Onyxes have a considerably longer history of use than black diamonds. They held cultural or religious significance amongst ancient cultures like the Romans, Persians, and in several portions of Renaissance Europe.

Besides, onyxes have also been a favorite of artists and architects who use it for cameos, intaglio, cut as a cabochon, or into beads.

However, today, the onyx has lost most of its prestige and is now a much more common and less prized gemstone.

Black diamonds, on the other hand, were only discovered in 1840. Since then, they have been the subject of the desire of a mostly niche audience. However, their popularity has been rising over the past couple of decades.

Which Should You Get?

Like with all gemstones, the deciding factor for choosing between these two will always be your personal preference. Both stones have distinct physical properties and appearances that hit differently from one buyer to another.

However, if you are after durability, diamonds are the obvious choice, and if you are on a tight budget, of the two gemstones, an onyx may be your only choice.

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