Disclosure:The example rings in this guide are from Ronatelli. Prices, ratings, and product details were read from ronatelli.com on October 29, 2026; the advice applies to any brand.
Black onyx is the classic stone of a man’s ring: a deep, even black against bright silver, at home with a T-shirt or a suit. It is also widely misunderstood. Most black onyx starts out grey and is turned black on purpose; it is harder than steel but no harder than the grit in household dust; and how well it keeps its polish depends as much on the setting as on the stone. This guide covers what onyx is, why it is treated, what can scratch it, how each setting holds it, how to wear it, and how to clean it without harming the stone or the silver.
Key takeaways
- A real gem, usually treated. Black onyx is chalcedony, a form of quartz. Naturally black chalcedony is rare, so most is turned black with a permanent treatment the Romans already used.
- Hard, not scratch-proof. At 6.5 to 7 on the Mohs scale it shrugs off steel, but the quartz grit in dust and sand is as hard or harder and dulls the polish over time.
- The setting decides the risk. A frame that wraps the edges protects the stone best; prongs and raised settings show more stone and take more knocks; pavé is the most delicate.
- Soap and water to clean it. Warm water, a drop of mild dish soap, and a soft brush. No foil bath, silver dip, steam, or ultrasonic.
- Keep heat away. Onyx is heat sensitive, so any repair with a torch means taking the stone out first.
In this guide What it is Is it dyed? Hardness Settings Faceted or smooth Wearing it Cleaning Examples FAQ
What black onyx is
Onyx is a variety of chalcedony, the fine-grained form of quartz that also includes agate and carnelian. Strictly speaking, onyx is banded: Sotheby’s describes it as a banded chalcedony whose layers can be white, grey, green, red, or orange-brown as well as black. In jewelry, though, “black onyx” means a stone that is an even black from edge to edge, and that is what you get in a men’s ring. The American Gem Trade Association (AGTA) notes that the ancient world called chalcedony of almost any color onyx, and that the Romans narrowed the word to black and dark brown. The name itself comes from the ancient Greek for “fingernail” or “claw.”
It has a long history on men’s hands. According to AGTA, no important Roman was without a seal, amulet, or signet ring carved from chalcedony, and the Victorians carved it into cameos and intaglios. The gem encyclopedia at Skyjems credits Queen Victoria’s long mourning for Albert, who died in 1861, with making jet, black onyx, and vulcanite the accepted materials for mourning jewelry. Most of it was Whitby jet, the Pitt Rivers Museum notes, though its collection includes a gold mourning ring with hair set behind onyx. In the 1930s, Art Deco jewelers prized polished onyx for its bold contrast, and today Skyjems lists cufflinks, signet rings, and tie pins among its uses in men’s jewelry.
Those are the associations a black onyx ring carries: the Roman seal ring, Victorian mourning, Art Deco contrast. Crystal sellers also credit it with strength and protection; those are beliefs rather than properties of the stone. Most men wear one for a simpler reason: black and silver go with everything.
Is black onyx dyed?
Almost always, and that doesn’t make it fake. “Pure black chalcedony is rare,” the gemologist Gary Roskin wrote in JCK, and Skyjems puts it more strongly: the overwhelming majority of black onyx in trade starts as grey, white, or banded agate or chalcedony and is turned black.
The method is ancient. AGTA cites the Roman writer Pliny describing it: the stone is soaked in sugar water, then boiled in strong acid, which burns the sugar inside the stone down to pure black carbon. Roskin calls the process “penetrating and permanent.” Today, AGTA adds, cobalt dye is another accepted way to color onyx.
Under the FTC’s Jewelry Guides, it is unfair or deceptive for a seller not to disclose a gemstone treatment that isn’t permanent, that creates special care requirements, or that has a significant effect on the stone’s value. If how your stone was colored matters to you, ask the seller; it is a fair question. Ronatelli describes the stones in six of its eleven rings as black onyx and doesn’t say how they were colored, so we don’t either. Its Marmo signet is different: Ronatelli describes its stone only as a square black stone with natural white veining and doesn’t name it.
Can you tell onyx from black glass or plastic at home? Not reliably. GIA researchers writing in Gems & Gemology count black, opaque materials among the most difficult gems to identify, because almost any material can be fashioned black and opaque and any porous one can be dyed; telling them apart often takes laboratory equipment. Buy from a seller who names the stone, and keep the product page.
How hard is black onyx?
Hard enough for a ring you wear every day. Onyx rates 7 on the Mohs scale of scratch hardness according to AGTA and JCK, and 6.5 to 7 according to Skyjems. As a chalcedony it is also tough: its fine, fibrous grain resists cracks better than a single quartz crystal does, Skyjems explains, and GIA lists chalcedony with diamond, corundum, and jadeite among the gems more resistant to abrasion and chipping. That combination is why it has been a ring stone for two thousand years.
Hard isn’t scratch-proof, though. “Polished black onyx scratches fairly easily and the scratches are noticeable,” Roskin writes. The culprit is everyday dust: the International Gem Society points out that it contains quartz, at 7 to 7.5 on the same scale, as hard as the onyx or harder. Wipe a dusty stone with a dry cloth and you drag that grit across the polish. Steel, at 5 to 6, won’t scratch it; sand and harder gems such as sapphire (9) and diamond (10) will.
The silver is the softer part. Pure silver is about 2.5 on the Mohs scale, and sterling, though a little harder, is still far softer than the stone, so on an onyx ring the band and the frame show wear long before the stone does. Our ring buying guide covers what daily wear does to the silver.
Chips are a different matter from scratches. They come from a sharp knock, and they start at an exposed corner or edge, which is where the setting comes in.
How the stone is held: four settings
The same stone can be well protected or exposed, depending on how the ring holds it. Ronatelli’s onyx rings show the four common ways.
A frame. A band of metal runs around the whole edge of the stone; jewelers call it a bezel. GIA’s guide to gemstone durability notes that a band of metal around the edge of a stone offers protection, and a frame is the setting to choose for a ring you will wear while using your hands. The Ragnar holds its faceted onyx in a square frame, and the Marmo sets its veined stone in a smooth silver one. Check that the frame sits tight against the stone all the way round.
Prongs. Small claws of metal grip the stone at its corners, so more of the stone shows and more light reaches it. The Troy is held by four arrow-tip prongs, the Arco by claw prongs. The trade-off is exposure: the edges between the prongs are uncovered, and the tips can catch on knitwear and pockets, as our comparison of the eleven rings notes. Check now and then that every tip still lies flat on the stone.
Raised. The stone sits high above the band on a built-up mount. On the Nero, in Ronatelli’s words, a faceted onyx is “raised high in an ornate setting,” and the product photos show it held at the corners by claws above an openwork base. A raised stone has the most presence and the most exposure: it is the first thing to meet a door frame. Treat it as a ring for the office and evenings out rather than the gym or the yard.
Pavé and accents. Dozens of tiny stones are set close together, each held by small beads of silver. The Agno’s hexagonal face is packed with them, the Horus’s winged motif rises from a bed of them, and the Troy, Arco, and Nero carry rows or borders of small onyx accents. Pavé is the most delicate setting, because each bead holds a very small stone; the jewelry brand Satinski warns that bending a ring too much can release its stones, especially on pavé designs. Look for an empty hole whenever you clean it.
Whatever the setting, if the stone moves or rattles, or a prong has lifted, stop wearing the ring until it is fixed; the cleaning section below covers repairs and the warranty.
Faceted or smooth?
Onyx is cut two ways. A faceted stone has flat, angled planes cut into its top that catch the light as sharp, dark flashes; the Ragnar, Arco, and Nero are faceted, in Ronatelli’s words. A smooth stone is polished into one even surface, flat or gently domed; in the product photos, the Troy’s onyx is smooth and domed, and the Marmo’s veined stone, which Ronatelli calls matte, is flat.
Faceting is the livelier, dressier look; a smooth stone is quieter and more classic. Either way, the polish is what shows wear, so the care is the same.
How to wear a black onyx ring
Black and silver is the strongest contrast in men’s jewelry, which is what makes an onyx ring so easy to wear. It works with black, grey, navy, and dark denim, and it looks right with a suit; against a white shirt cuff it is at its most graphic.
A statement onyx ring sits well on the ring finger or the middle finger of your right hand, leaving the left for a wedding band. A stone signet such as the Agno or Horus follows the signet traditions in our signet ring guide, including the pinky. One onyx ring per hand is plenty; if you want a second ring, make it a plain silver band.
Take it off for the gym, yard work, the beach, and anything with sand or grit, and for cleaning with household chemicals. Ronatelli’s own care advice is to keep perfume, aftershave, and lotion off your jewelry and to put it on last, and its warranty excludes damage from harsh chemicals such as chlorine and bleach. Water won’t harm the stone or the silver; if the ring gets wet, dry it with a soft cloth, as Ronatelli advises. AGTA’s advice for onyx, as for all fine jewelry, is to take it off before you sleep.
How to clean a black onyx ring
Soap and water does it. Lay the ring in warm (not hot) water with a drop of mild dish soap for a few minutes, work a soft brush around the stone and into the setting, rinse it in clean water, and dry it completely with a soft cotton cloth. That is the method AGTA and Skyjems recommend for onyx, and the one our cleaning guide gives for hard stones. Rinse before you rub: water first, then the cloth, so you don’t drag dust across the polish.
To brighten the silver, use a polishing cloth on the band and the frame only, and keep it off the stone. On the Arco, Nero, Horus, and Agno, the recesses of the engraving are darkened on purpose, so run the cloth over the high points only, as our guide to oxidized silver explains.
| Method | On an onyx ring | Why |
|---|---|---|
| Warm water, mild dish soap, soft brush | On an onyx ringYes | WhyLifts skin oil and grime from the stone and the setting |
| Soft cotton cloth | On an onyx ringYes, after rinsing | WhyDries and shines; rinse first so it doesn’t drag grit across the stone |
| Polishing cloth | On an onyx ringSilver only | WhyBrightens the band and frame; keep it off the stone and the darkened recesses |
| Foil bath or silver dip | On an onyx ringNo | WhyOur cleaning guide keeps stone-set pieces out of both, and they strip darkened recesses |
| Ultrasonic cleaner | On an onyx ringNo | WhyJCK considers it safe for permanently treated onyx, but you can’t know how yours was treated, and Skyjems advises against it if dye is suspected |
| Steam cleaner | On an onyx ringNo | WhySkyjems doesn’t recommend it, and heat is onyx’s weak point |
| Toothpaste or baking soda paste | On an onyx ringNo | WhyAbrasive: leaves permanent scratches on polished silver |
| Bleach, chlorine, or acetone | On an onyx ringNo | WhyAttack the silver and the stone, and Ronatelli’s warranty excludes chemical damage |
Keep heat away from the stone. Roskin notes that black onyx is heat sensitive, so a jeweler should take the stone out before retipping a prong or sizing the ring, and our cleaning guide warns that hot water can crack stones. Ronatelli’s rings are adjustable, so there is no sizing to do; our guide to adjustable rings covers fitting a stone ring without stressing the setting.
If a stone works loose or goes missing, stop wearing the ring and keep any pieces. Ronatelli’s lifetime warranty covers verified manufacturing defects and asks for photos or a video with every claim. It excludes repairs by anyone other than Ronatelli’s own technicians, so contact Ronatelli before you take the ring to a local jeweler, and it also excludes general wear, scratches, and missing pieces that can’t be verified as a manufacturing issue.
Store it on its own, in its box or a soft pouch, as Ronatelli suggests. A diamond or sapphire ring in the same tray will scratch it.
Black onyx rings at Ronatelli
Six of the eleven rings in Ronatelli’s ring collection are set with black onyx, from $129 to $169, all in 925 sterling silver and all adjustable. The Marmo is listed for contrast: its stone is black with white veining, and Ronatelli doesn’t name it.
| Ring | Stone | Setting | Price | Rating (reviews) |
|---|---|---|---|---|
| Ragnar: Square Black Onyx Ring | StoneFaceted, square | SettingSquare frame | Price$149 | Rating (reviews)4.7 (93) |
| Troy: Black Onyx Ring | StoneSmooth, domed, with onyx accents | SettingArrow-tip prongs | Price$149 | Rating (reviews)4.9 (17) |
| Arco: Faceted Black Onyx Ring | StoneLarge, faceted, with onyx accents | SettingClaw prongs | Price$169 | Rating (reviews)3.8 (4) |
| Nero: Ornate Black Onyx Ring | StoneFaceted, with onyx accents | SettingRaised | Price$149 | Rating (reviews)4.8 (4) |
| Horus: Faravahar Signet Ring | StoneSmall onyx stones under a winged motif | SettingPavé | Price$139 | Rating (reviews)4.8 (5) |
| Agno: Hexagonal Signet Ring | StoneSmall onyx stones filling a hexagonal face | SettingPavé | Price$129 | Rating (reviews)4.7 (3) |
| Marmo: Veined Stone Signet Ring | StoneBlack with white veining, not named | SettingSquare frame | Price$129 | Rating (reviews)4.0 (2) |
For a first onyx ring, or one you will wear every day, the Ragnar is the safe choice: its frame protects the stone best, and with 93 reviews at 4.7 it has by far the longest record in the collection. The Troy is the dressier pick, with a smooth stone and the highest average of any ring with more than a handful of reviews. The Arco and Nero put the most stone on show, and the Agno and Horus put onyx into a signet. Our comparison of all eleven rings covers the whole collection, and our guide to adjustable rings explains the one-size fit.
FAQ
Is black onyx a real gemstone?
Yes. It is chalcedony, a fine-grained form of quartz, rated about 7 on the Mohs scale. Most black onyx is turned black by a permanent treatment, which is standard in the trade.
Is black onyx dyed?
Usually. Naturally black chalcedony is rare, so most black onyx starts as grey or banded chalcedony and is turned black, traditionally with sugar and acid, which leaves carbon in the stone and is permanent. Ask the seller if you want to know how a particular stone was treated.
Does black onyx scratch easily?
Not from steel, but its polish can pick up fine scratches from dust and sand, which contain quartz as hard as the stone or harder, and from harder gems such as diamond and sapphire. Rinse grit off before you wipe it, and store it on its own.
Can you wear a black onyx ring every day?
Yes, especially in a frame setting like the Ragnar’s. Take it off for the gym, yard work, the beach, and cleaning, and check the prongs and small stones now and then.
Can a black onyx ring get wet?
Yes. Water doesn’t harm onyx or sterling silver; dry it afterward. Take it off for the pool or hot tub, though: chlorine is one of the harsh chemicals Ronatelli’s warranty excludes.
How do you clean a black onyx ring?
Warm water, a drop of mild dish soap, and a soft brush, then rinse and dry it with a soft cloth. Skip the foil bath, silver dips, steam, and ultrasonic cleaners.
Is black onyx the same as jet?
No. Jet is a lightweight mineraloid formed from ancient wood, easy to carve and polish, and was the classic Victorian mourning material. Onyx is a quartz, about 7 on the Mohs scale.
Bottom line
Black onyx earns its place on a man’s hand: a real, tough quartz with two thousand years of rings behind it, almost always treated to its even black, and hard enough for every day. Choose the setting for how you live: a frame for daily wear and work with your hands, prongs or a raised stone for presence, pavé for a signet face you will treat with a little care. Clean it with soap and water, rinse before you wipe, and keep it away from heat, chemicals, and harder stones, and it will look the part for years.
From the collection
Men’s sterling silver rings by Ronatelli
Eleven handmade 925 rings, $129 to $169, from a chain-link band to a black onyx statement ring. Every one is adjustable.
Related guides
Ronatelli’s stone and setting descriptions, care advice, prices, ratings, and warranty terms were read from its ring product, FAQ, and warranty pages on October 29, 2026, and may have changed since; smooth and faceted stones and the settings are also from the product photos. What onyx is, how it is treated, and how to clean it follow AGTA’s onyx and chalcedony pages, Gary Roskin’s “Black Chalcedony” in JCK, Skyjems’ gem encyclopedia, and Sotheby’s “The A-Z of Jewelry: O is for Onyx”; identification follows Johnson, McClure, and DeGhionno in Gems & Gemology (Winter 1996); disclosure follows the FTC’s Jewelry Guides (16 CFR 23.24). Hardness and dust follow the International Gem Society, and the hardness of pure silver KnowledgeDoor’s elements handbook; settings follow GIA’s “Gemstone Durability: Design to Display” and Satinski; mourning jewelry follows the Pitt Rivers Museum. Read our editorial policy.
