Original Onyx Stone (Onex Ratna): Black and Green Onyx Price Guide India (2026)
“Onyx (Onex Ratna) is chalcedony, sold in India as green onyx, the Emerald substitute, and black onyx for Shani and Rahu. Learn how onyx is coloured, how to tell it from glass and onyx marble, and what it really costs.”
Onex Ratna, or onyx, is a variety of chalcedony — microcrystalline quartz — valued for centuries for carving, seals and jewellery, and linked in many traditions with protection. In India two kinds are sold: green onyx, the traditional substitute for Emerald (Panna), and black onyx, associated with Shani and Rahu. What most buyers are not told is that nearly all solid black onyx, and much green onyx, is chalcedony that has been coloured — a permanent, standard trade practice that should simply be disclosed. This guide explains how onyx is coloured, how to tell it from glass, plastic and "onyx marble", what it costs, and how to buy it with confidence.
Quick answers: Onyx is chalcedony (Mohs 6.5–7, SG about 2.60). Most solid black onyx is grey chalcedony blackened by a sugar-and-acid treatment; much green onyx is dyed with chromium or nickel salts. "Onyx marble" is a different, much softer stone (calcite). Ratna Gems sells natural Indian green onyx at ₹150 to ₹250 per carat with an independent laboratory report (October 2026) — see the Onyx collection.
Onyx Gemological Specifications
| Mineral Family | Chalcedony (Microcrystalline Quartz) |
| Chemical Formula | SiO₂ (Silicon Dioxide) |
| Hardness | 6.5 - 7 on the Mohs Scale |
| Specific Gravity | About 2.60 |
| Refractive Index | About 1.53 - 1.54 (usually read as a single value) |
| Polariscope Character | AGG (Aggregate — remains constantly bright under crossed polarizers) |
| Primary Origins | Brazil, Uruguay, India and elsewhere |
What is Onyx Stone (Onex Ratna)?
Onyx is a microcrystalline (or cryptocrystalline) variety of chalcedony quartz. Gemologically, the difference between Agate and Onyx lies in their banding: Agate features concentric, curved banding, whereas Onyx features straight, parallel banding. Historically, these high-contrast parallel layers made Onyx the ultimate medium for carving cameos and signet rings, and sealing wax was said not to stick to it.
The Chemistry of Onyx Dyeing Treatments
Because solid, natural black or intense emerald-green chalcedony is extremely rare in nature, the gem trade colours chalcedony using permanent treatments, refined in the gem-cutting town of Idar-Oberstein, Germany, in the 19th century:
- Black Onyx (Sugar-Acid Carbonization): Gray chalcedony is soaked in a sugar or honey solution for weeks. It is then boiled in concentrated sulfuric acid. The acid acts as a dehydrating agent, carbonizing/charring the sugar to trap microscopic particles of black carbon soot within the stone's silica pores. This treatment is permanent and stable.
- Green Onyx (Chrome & Nickel Salts): Porous chalcedony is soaked in chromium chloride or nickel nitrate solutions to produce a deep green hue. Through a Chelsea colour filter, chrome-dyed chalcedony usually shows pink or red, while chrysoprase, coloured naturally by nickel, stays green (see the note below on what the filter can and cannot prove).
Onyx vs. "Onyx Marble"
Know the difference: true onyx is chalcedony, at Mohs 6.5–7. The decorative and interior-design trade uses "onyx marble" (or "Mexican onyx") for banded calcite or aragonite, which is only about Mohs 3–4 and is attacked by mild acids. It is a different stone entirely and should never be sold as onyx gemstone. A laboratory separates them instantly; do not scratch or acid-test a stone you intend to buy.
How to Identify Original Onyx Stone
A laboratory report is the reliable answer. These checks help you understand what the laboratory is looking at:
- Polariscope (aggregate reaction): chalcedony is made of countless microscopic quartz crystals, so between crossed polarising filters it stays bright as it is turned. Glass usually stays dark, and plastic often shows strain patterns.
- Touch: stone feels cooler to the touch than plastic, which warms quickly in the hand. This separates stone from plastic only; glass feels cool too.
- Magnification: under a 10x loupe, look for natural banding or texture. Mould lines and round gas bubbles are signs of glass or plastic imitations.
Onyx Stone Price in India (2026)
Onyx is an affordable gem, which is why green onyx is the most practical way to wear a Mercury stone of the full traditional Ratti weight. Price depends on depth and evenness of colour, translucency, polish and cut. At Ratna Gems, natural Indian green onyx is priced at ₹150 or ₹250 per carat depending on the series, with an independent laboratory report. These are stones in stock in October 2026:
Ratna Gems Green Onyx Prices (in stock, October 2026)
| Weight | Shape | Price |
|---|---|---|
| 5.01 carat (5.51 ratti) | Oval | ₹752 (₹150 per carat) |
| 6.38 carat (7.01 ratti) | Octagon | ₹957 (₹150 per carat) |
| 5.02 carat (5.52 ratti) | Octagon | ₹1,255 (₹250 per carat) |
| 6.28 carat (6.90 ratti) | Octagon | ₹1,570 (₹250 per carat) |
Onyx in Vedic Tradition
Onyx is widely worn in India as an upratna (substitute gemstone). The customs below are the ones most often followed; whether a stone suits you, and at what weight, is for your own astrologer or Pandit ji to advise.
1. Green Onyx for Mercury (Budh)
Green Onyx is a traditional upratna, or substitute stone, for Emerald (Panna), and is associated with Mercury (Budh), the planet traditionally linked with intellect, speech and trade. By custom, a substitute is worn at a larger weight than the main stone.
- Traditional customs: set in silver and worn on the little finger of the working hand, first worn on a Wednesday morning during Shukla Paksha. The Mercury mantra linked with it is "Om Bum Budhaya Namah" (ॐ बुं बुधाय नमः).
- Usual weight: about 1 Ratti per 10 kg of body weight by custom (1 pakki Ratti = 0.91 carat). Every Ratna Gems listing gives the weight in both carats and ratti.
Read this before buying green onyx — it is the point most sellers skip. The great majority of green onyx on the world market is dyed chalcedony, and most of it starts as grey or white Brazilian agate that is coloured with chrome or nickel salts. Natural green chalcedony does exist — but it usually looks different, and that difference is the thing to learn.
Judge it by colour behaviour, not by price. Dyed material is uniformly, vividly green, because a dye bath colours everything evenly and the whole point of the process is to produce a consistent stone. Naturally coloured green chalcedony is more variable: the green shifts in depth across the stone, it is often softer or more olive in tone, and it does not look manufactured. So the instinct most buyers bring to this — that a deeper, more even green must be the better stone — is exactly backwards here. Variation is usually the mark of natural colour; perfect uniformity is usually the mark of the dye bath.
What the colour filter actually tells you. A Chelsea colour filter is the standard first check: chrome-coloured green stones appear pink or red through it, while nickel-coloured ones stay green. Be careful how you read that, though, because it detects the element rather than the method — most green dye is chromium based, so red through the filter points to dye, but naturally chrome-bearing chalcedony would also read red. The filter narrows the question in seconds and costs very little; it does not close it. What closes it is a loupe and a laboratory: under 10x magnification, dye concentrates in fractures, along banding and in the porous zones, and it often looks paler inside a drill hole or chip, whereas natural colour sits evenly through the body of the stone and ignores the cracks entirely. Buyers who follow tradition generally avoid dyed stones, so if that matters to you, this is the question that decides the purchase. Ask the seller in writing whether the colour is dyed, and whether the stone has been checked under a filter. A seller who cannot answer either question is not the right seller for you.
2. Black Onyx / Sulemani Akik for Saturn (Shani) & Rahu
In Sufi and Islamic traditions, black agate and banded onyx are known as Sulemani Akik, named after Prophet Sulaiman (Solomon), and are worn as a guard against the evil eye (nazar). In Vedic tradition, black onyx is associated with Saturn (Shani) and Rahu. By custom, it is set in silver and first worn on the middle finger on a Saturday evening. The mantra linked with it is "Om Sham Shanaishcharaya Namah" (ॐ शं शनैश्चराय नमः).
Historical Legends of Sardonyx
Sardonyx (bands of red-brown sard and white onyx) has a famous military history. Roman soldiers are said to have worn sardonyx rings and amulets engraved with Mars or Hercules, for courage in battle. Romans also favoured it for seals, as hot wax was said not to stick to it. It was the chosen material for grand imperial State Cameos (like the Gemma Augustea), which show Roman emperors as divine conquerors. Read more in our Agate (Hakik) guide, onyx's closest relative.
How to Care for Onyx Jewelry
- Chemical Exposure: avoid harsh household chemicals such as bleach or ammonia; on coloured onyx they can affect the colour.
- Cleaning: use warm, soapy water and a soft brush; avoid ultrasonic and steam cleaners on dyed stones.
- Storage: Store your Onyx rings separately from harder gemstones (like Sapphires or Rubies) to protect them from surface scratches.
Why Buy Onyx from Ratna Gems?
Every onyx from Ratna Gems comes with:
- An Independent Lab Report: natural chalcedony, never plastic or glass, with a free report from an independent, ISO-certified laboratory; a GII, IIGJ or IGI report can be added on the product page, priced by carat weight.
- Clear Listings: weight in carats and ratti, origin and price per carat stated on every listing.
- 7-Day Returns: return an unused stone in its original condition within 7 days of delivery, as set out in our return policy.
Frequently Asked Questions
What is Onex Ratna (Onyx stone)?
Onex Ratna is the Hindi trade name for Onyx — a variety of chalcedony (microcrystalline quartz). True Onyx has parallel bands of black and white, but "Black Onyx" and "Green Onyx" commonly refer to solid-colored dyed chalcedony. It is valued for its appearance and for its traditional associations.
What is the price of Onyx stone in India?
Onyx is one of the more affordable gems. At Ratna Gems, natural Indian green onyx costs ₹150 or ₹250 per carat with an independent laboratory report (October 2026); for example, a 6.38 carat (7.01 ratti) stone costs ₹957. See the Onyx collection for the stones in stock.
Is Black Onyx always dyed?
Almost always. Nearly all solid black onyx is grey chalcedony or agate blackened by a sugar-and-acid treatment. The colour is permanent and the practice is accepted in the trade, provided it is disclosed. Natural solid black chalcedony is very rare.
How to identify real Onyx from fake?
Between crossed polarising filters, chalcedony stays bright as it is turned, while glass usually stays dark; stone also feels cooler than plastic. A laboratory report is the reliable answer — every Ratna Gems stone ships with one. Avoid scratch tests, which can damage the stone.
What is the difference between Black Onyx and Green Onyx?
Both are chalcedony. Solid black onyx is almost always treated to be black; green onyx may be dyed or naturally coloured, so ask which. They have similar hardness (6.5-7) and durability. In Vedic tradition, Green Onyx is a substitute for Emerald (Mercury), while Black Onyx is linked with Saturn and Rahu.
Which planet is Onyx associated with?
In Vedic tradition, green onyx is associated with Mercury (Budh) as a substitute for Emerald, and black onyx (Sulemani Akik) with Saturn (Shani) or Rahu. By custom, it is set in silver and worn on the little finger for Mercury or the middle finger for Saturn. Whether to wear it is for your own astrologer or Pandit ji to advise.
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