Irradiated
Irradiation changes a gem's colour by exposure to radiation such as gamma rays, an electron beam or neutrons. Irradiation is usually followed by annealing to stabilise the colour. Irradiated material must be disclosed.
On this page
Naming rule
- Naming rule
- Irradiated [material name]
- Market differences and mutual recognition
- GB/T 16552 makes one exception: irradiated rock crystal counts as an optimization, while irradiation of everything else is classed as a treatment and has to be named. CIBJO Gemstone Book 2022 describes the result to buyers as “Artificially irradiated”. Residual radioactivity and licensing are national matters outside the documents compared here.
Gem treatments compares how every treatment on this site is named and what each must disclose.
Where the treatment acts (schematic)
Changes colour by irradiation (gamma rays, electron beam, neutrons etc.); usually followed by annealing to stabilise the colour.
- Colourless topaz
- Irradiation (schematic; not the type or dose of radiation)
- Yellow to brown after irradiation
- Heating
- Blue after heating (depth of colour schematic)
If you reuse this animation, please credit LumaLark Wiki and link to this pageLicense: CC BY 4.0
Scene-by-scene transcript (4 scenes, with sources)
The caption of each scene in the animation above (the first scene lists its three panel captions), with sources.
Scene 1Irradiation (colourless topaz as the example)
Before: The usual starting material is colourless topaz, which is also topaz's most common natural colour.
During: The stone is irradiated and, in most cases, then heated.
After: How deep the colour goes depends on the radiation source.
Treated zone: inside the stone; depth depends on the source
Scene 2Process conditions
The stone is irradiated and, in most cases, then heated. The three major types of radiation source are gamma rays from cobalt-60, high-energy electrons from a linear accelerator, and neutrons from a nuclear reactor; after irradiation the stone is yellow to brown, and at higher gamma doses an olive-green component may be visible. The heating that removes the brown is usually at 200–300°C for one to two hours, and heating in air is adequate; at about 500°C the blue itself begins to fade. Neutron-treated topaz generally needs no heating to remove brown.
The usual starting material is colourless topaz, which is also topaz's most common natural colour. Not all colourless topaz responds to treatment; sometimes only one part of a crystal changes colour.
Scene 3How it works
The yellow-to-brown and the blue colours are both colour centres, formed when radiation interacts with electrons on defects (of unknown nature, the 1985 paper says). On heating, the electrons displaced by the radiation return to where they came from and the colour fades: the unstable yellow-to-brown goes within an hour or less at temperatures as low as 200°C, the stable yellow-to-brown needs a few hours at 200–400°C, and the stable blue needs about 500°C. Heating only removes the yellow to brown and reveals any blue that may be present; not every stone irradiated to yellow or brown turns blue. A 2023 GIA paper, citing 2007 work, says oxygen hole centre defects produce the brown or blue colours, though whether additional defects contribute to the blue remains uncertain.
Scene 4After treatment and how it is detected
How deep the colour goes depends on the radiation source. Gamma rays are very penetrating and colour the stone uniformly if the material is uniform; neutrons penetrate excellently and the colours are usually uniform and deep; energetic electrons have limited penetration, so the colouring is most intense at the surface. Because the topaz itself varies in impurities and defects, the colour is frequently not uniform, and it can vary even within a single stone.
No routine gemological test can determine whether the colour of a blue topaz is natural or the result of treatment, and treated stones show the same absorption spectra as natural stones of the same colour; a 2010 GIA review still calls these treatments undetectable, and blue topaz on the market is assumed to have been irradiated. Of the three methods, reactor (neutron) and linear-accelerator (electron) treatment can both induce residual radioactivity, the reactor posing the more serious problem; gamma-ray treatment does not make stones radioactive. Radioactive stones are held until they decay below the exemption level: in one study most neutron-irradiated blue topaz samples were already below it when first measured about three months after irradiation, while a few with more impurities needed several years of quarantine.
Sources
- Altering the Color of Topaz, by Kurt Nassau (Gems & Gemology, Spring 1985, Vol. 21, No. 1)
- Gemstone Enhancement and Its Detection in the 2000s, by Shane F. McClure, Robert E. Kane and Nicholas Sturman (Gems & Gemology, Fall 2010, Vol. 46, No. 3)
- The Radioactive Decay Pattern of Blue Topaz Treated by Neutron Irradiation, by Jian Zhang et al. (Gems & Gemology, Winter 2011, Vol. 47, No. 4)
- Backgrounder on Irradiated Gemstones (U.S. Nuclear Regulatory Commission, March 2024)
- Topaz from Mason County, Texas, by Roy Bassoo et al. (Gems & Gemology, Winter 2023, Vol. 59, No. 4)
- Gemstone Irradiation and Radioactivity, by Charles E. Ashbaugh III (Gems & Gemology, Winter 1988, Vol. 24, No. 4)
How the naming authorities record it
This table scrolls sideways on narrow screens.
| Column | Value |
|---|---|
| Description | Changes colour by irradiation (gamma rays, electron beam, neutrons etc.); usually followed by annealing to stabilise the colour. |
| GIA code | IR |
| LMHC number / note | R (CIBJO Gemstone Book 2022 Annex B, clause 7.2: Artificial irradiation); LMHC has no matching Information Sheet |
| GB/T category | Treatment (GB/T 16552-2017 §5.4.1 Table 1: irradiation is classified as treatment, with the remark that this method is classified as optimization for quartz; representation method at §5.4.2.2). |
| CIBJO disclosure requirement | CIBJO Gemstone Book 2022 §5.47 defines Irradiated / Irradiation. CIBJO Gemstone Book 2022 §4.2.5.2 sets out the disclosure method (trade code R per Annex B, clause 7.2; CIBJO does not use "IR"). |
| FTC regulatory citation | §23.24 general rule: disclosure is required if the treatment is not permanent (a), creates special care requirements (b), or has a significant effect on value (c). §23.24 names no individual treatment, so Part 23 does not say which of (a)–(c) irradiation meets. |
| RAL / German declaration | No public source text: RAL 560 A5 is a paid document not on file on this site, so no RAL/DGemG wording is shown (unchecked) |
| JJA/AGL (Japan) treatment disclosure | JJA/AGL 2025 §1-2-1 lists irradiation (item ④) among the treatments applied to natural stones; §2-1-1: the treatment is to be stated to the extent it can be known. |
| AGTA code | R — irradiation with neutrons, gamma rays or beta particles to alter colour (GIM 17th ed., p.V). The 17th edition's code list has no "IR". Consumer disclosure must be in plain language; codes alone are not sufficient (p.III). |
| Gem-A position | The Gem-A By-Laws have no irradiation-specific rule. §7.e.iii: before purchase the buyer should be told if the stone is known to have been treated and, where relevant, how that may affect its durability; §7.b: CIBJO guidelines and definitions are taken as best practice. |
| Naming rule | Irradiated [material name] |
| Disclosure requirement | Must be disclosed. Stability under irradiation varies by material: irradiated blue topaz keeps a stable colour and irradiated smoky quartz or coloured diamond can, but in some materials the irradiated colour fades in light or heat; colour stability must be pointed out. |
| Typical materials treated | Blue topaz (most typical), smoky quartz, coloured diamond, tourmaline, morganite |
| Market differences and mutual recognition | GB/T 16552 makes one exception: irradiated rock crystal counts as an optimization, while irradiation of everything else is classed as a treatment and has to be named. CIBJO Gemstone Book 2022 describes the result to buyers as “Artificially irradiated”. Residual radioactivity and licensing are national matters outside the documents compared here. |
Materials on which it is recorded
How lab reports word it, by material
The standard report wording (LMHC) for this treatment is set out on these entries and sections:
The laboratory testing page's LMHC index lists every LMHC information sheet on report wording.
CIBJO definitions
- Irradiated / Irradiation
exposing gemstones, diamonds, pearls, cultured pearls and artificial products to any form of radiation which is controlled wholly or partially by man, usually to alter their appearance. See clause 4.2.5.2.
CIBJO Blue Book — Official Gemstone Book (Coloured Stone Commission 2022) (CIBJO): §5.47, p.25
exposing pearls, cultured pearls, diamonds, gemstones, synthetic stones and artificial products to any form of radiation which is controlled wholly or partially by man, usually to alter their appearance.
CIBJO Blue Book — Pearl Book (Pearl Commission 2024-1) (CIBJO): §5.102, p.32
The books word this differently; each wording is given with its source.
Definitions are quoted verbatim from the cited CIBJO Blue Book; […] marks an excerpt, and the full definition is at the cited clause.
Materials listed for this method in GB/T 16552-2017 Table B.1
This table scrolls sideways on narrow screens.
| Material (row) | Method | Effect | Category |
|---|---|---|---|
| Diamond | Irradiation (often followed by heating) | Changes colour | Treatment |
| Sapphire | Irradiation | Changes colour | Treatment |
| Cat’s-eye | Irradiation | Improves the eye line, colour and other aspects of appearance | Treatment |
| Aquamarine | Irradiation | Changes colour | Treatment |
| Beryl | Irradiation | Changes colour | Treatment |
| Tourmaline | Irradiation | Changes colour | Treatment |
| Zircon | Irradiation | Changes colour | Treatment |
| Topaz | Irradiation | Changes colour | Treatment |
| Rock Crystal | Irradiation | Changes colour | Optimization |
| Feldspar | Irradiation | Changes colour | Treatment |
| Scapolite | Irradiation | Changes colour | Treatment |
| Spodumene | Irradiation | Changes colour | Treatment |
| Calcite | Irradiation | Changes colour | Treatment |
| Euclase | Irradiation | Changes colour | Treatment |
| Fluorite | Irradiation | Changes colour | Treatment |
| Cultured Pearl (Pearl) | Irradiation | Changes colour | Treatment |
| Amber | Irradiation | Changes colour | Treatment |
JJA/AGL table entries relating to this treatment
This table scrolls sideways on narrow screens.
| Gem name | Colour | As written in the table | Entry on this site | Page |
|---|---|---|---|---|
| Smoky Quartz | brown | irradiation | Smoky Quartz | p.10 |
| Green Quartz | green | irradiation | Green Quartz, Prasiolite / Green Quartz | p.10 |
| Kunzite | pink | irradiation | Kunzite | p.14 |
| Diamond | any colour | irradiation | Diamond | p.14 |
| Black Diamond | black | irradiation | Diamond | p.14 |
| Blue Topaz | blue | irradiation | Topaz, Irradiated Blue Topaz | p.14 |
| [colour] Tourmaline | pink to red | irradiation | Rubellite | p.14 |
| [colour] Fluorite | blue | irradiation | Fluorite | p.16 |
| Morganite | light reddish orange to purplish pink | irradiation | Morganite | p.16 |
Other treatments
Sources
This table scrolls sideways on narrow screens.
| Authority | Document | Version | Clause | Source |
|---|---|---|---|---|
| GB/T | GB/T 16552-2017 | 2017 | §5.4.1 | Source |
| GB/T | GB/T 16552-2017 | 2017 | Table 1 | Source |
| GB/T | GB/T 16552-2017 | 2017 | §5.4.2.2 | Source |
| CIBJO | CIBJO Gemstone Book | 2022 | §5.47 | Source |
| CIBJO | CIBJO Gemstone Book | 2022 | §4.2.5.2 | Source |
| CIBJO | CIBJO Gemstone Book | 2022 | Annex B, clause 7.2 | Source |
| FTC | 16 C.F.R. Part 23 | §23.24 | Source | |
| JJA/AGL | JJA/AGL definitions and nomenclature for gems (Japanese-language document, no official English title) | issued January 2015, revised November 2025 | §1-2-1 | Source |
| JJA/AGL | JJA/AGL definitions and nomenclature for gems (Japanese-language document, no official English title) | issued January 2015, revised November 2025 | §2-1-1 | Source |
| AGTA | AGTA Gemstone Information Manual | 17th edition, August 2026 | p.V (R) | Source |
| AGTA | AGTA Gemstone Information Manual | 17th edition, August 2026 | p.III | Source |
| Gem-A | Gem-A By-Laws §7 Code of Practice (Gem Code) | 2009 revision | §7.e.iii | Source |
| Gem-A | Gem-A By-Laws §7 Code of Practice (Gem Code) | 2009 revision | §7.b | Source |
What the eye can and cannot tell
Colour by itself settles nothing here. Blue topaz, smoky quartz, coloured diamond, tourmaline and morganite are the materials this process reaches, usually with annealing afterwards to stabilise the colour. Residual radioactivity is not something appearance can report: it is established by measurement, and the licensing and limit values that go with it are set out alongside.
What to ask for on the report
Who holds the licence for this batch? Neutron-irradiated topaz requires a US NRC licence for initial distribution in the United States, and before sale the goods must also meet the applicable residual-radioactivity limits.
Before you buy: what to check
Work through these in order before paying. None of them replaces a laboratory report; they decide whether you need one.
Colour by itself settles nothing here. Blue topaz, smoky quartz, coloured diamond, tourmaline and morganite are the materials this process reaches, usually with annealing afterwards to stabilise the colour. Residual radioactivity is not something appearance can report: it is established by measurement, and the licensing and limit values that go with it are set out alongside.
- Who holds the licence for this batch? Neutron-irradiated topaz requires a US NRC licence for initial distribution in the United States, and before sale the goods must also meet the applicable residual-radioactivity limits.
- Must be disclosed. Stability under irradiation varies by material: irradiated blue topaz keeps a stable colour and irradiated smoky quartz or coloured diamond can, but in some materials the irradiated colour fades in light or heat; colour stability must be pointed out.
Questions about this treatment?
Disclosure practice for this treatment differs between authorities and markets, and a report does not always say what was done.