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Gemstone irradiation
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<h2 id="radioactivity-and-regulations">Radioactivity and regulations</h2> <p class="note">See also: <a href="/facts/Induced_radioactivity/8BW4GmHe">Induced radioactivity</a> and <a href="/facts/Neutron_activation/FXwq3HUs">Neutron activation</a></p> <p>The term <i>irradiation</i> broadly refers to the exposure of matter to <a href="/facts/Subatomic_particle/tMEzcTWQ">subatomic particles</a> or <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic radiation</a> across the entire spectrum, which includes—in order of increasing <a href="/facts/Frequency/QUSbPaW8">frequency</a> and decreasing <a href="/facts/Wavelength/kcJU0ymz">wavelength</a>—<a href="/facts/Infrared/44XdJNcc">infrared</a>, visible light, <a href="/facts/Ultraviolet/kncBUqn5">ultraviolet</a>, <a href="/facts/X-ray/wseP79cN">X-rays</a>, and <a href="/facts/Gamma_ray/5Drf913J">gamma rays</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Certain natural gemstone colors, such as blue-to-green colors in <a href="/facts/Diamond/IBUdnd1y">diamonds</a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> or red colors in <a href="/facts/Zircon/84APfbLt">zircon</a>,<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> are caused by exposure to natural radiation in the earth, which is usually <a href="/facts/Alpha_particle/dzNMs9WP">alpha</a> or <a href="/facts/Beta_particle/x8b3ttLn">beta particles</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> The limited penetrating ability of these particles result in partial coloring of the gemstone's surface.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Only high-energy radiation such as gamma rays or <a href="/facts/Neutron/oRCM1geb">neutrons</a> can produce fully saturated body colors,<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> and the sources of these types of radiation are rare in nature, which necessitates the artificial treatment in jewelry industry. The process, particularly when done in a nuclear reactor for neutron bombardment, can make gemstones radioactive.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> Neutrons penetrate the gemstones easily and may cause visually pleasing uniform coloration, but also penetrate into the <a href="/facts/Atomic_nucleus/orpIm5Xl">atomic nucleus</a> and cause the <a href="/facts/Excited_state/czcLYNnr">excited nucleus</a> to <a href="/facts/Radioactive_decay/Ya6FVjt4">decay</a>, thereby inducing radioactivity.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> So neutron-treated gemstones are set aside afterward for a couple of months to several years to allow the residual radioactivity to decay,<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> until they reach a safe level of less than 1 <a href="/facts/Curie_(unit)/LeS60aVv">nanocurie</a> per <a href="/facts/Gram/CNAPqWKz">gram</a> (37 <a href="/facts/Becquerel/4C3yrsqp">Bq</a>/g) to 2.7 nanocuries per gram (100 Bq/g) depending on the country.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p><p>The first documented artificially irradiated gemstone was created by English chemist <a href="/facts/William_Crookes/q8U8VVwR">William Crookes</a> in 1905 by burying a colorless diamond in powdered <a href="/facts/Radium_bromide/0nKXeMlv">radium bromide</a>.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> After having been kept there for 16 months, the diamond became olive green.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> This method produces a dangerous degree of long-term radioactive contamination and is no longer in use.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> Some of these radium-treated diamonds—which are still occasionally put on sale and can be detected by <a href="/facts/Particle_detector/rYj0qKtA">particle detectors</a> such as the <a href="/facts/Geiger_counter/3xDNYh7I">Geiger counter</a>,<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> the <a href="/facts/Scintillation_counter/DFB1gpJv">scintillation counter</a>,<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> or the <a href="/facts/Semiconductor_detector/HzvpIobR">semiconductor detector</a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a>—are so high in radiation emission that they may darken <a href="/facts/Photographic_film/37aFq6ls">photographic film</a> in minutes.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> </p><p>The concerns for possible health risks related to the residual radioactivity of the irradiated gemstones led to government regulations in many countries.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> In the United States, the <a href="/facts/Nuclear_Regulatory_Commission/tbC56grX">Nuclear Regulatory Commission</a> (NRC) has set strict limits on the allowable levels of residual radioactivity before an irradiated gemstone can be distributed in the country.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> All neutron- or electron beam-irradiated gemstones must be tested by an NRC-licensee prior to release for sales; however, when treated in a cobalt-60 gamma ray facility, gemstones do not become radioactive and thus are not under NRC authority.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> In India, the <a href="/facts/Board_of_Radiation_and_Isotope_Technology/Rx0KAbzs">Board of Radiation and Isotope Technology</a> (BRIT), the industrial unit of the <a href="/facts/Department_of_Atomic_Energy/TcjRsp9g">Department of Atomic Energy</a>, conducts the process for private sectors.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> In Thailand, the <a href="/facts/Office_of_Atoms_for_Peace/IKS0H9Em">Office of Atoms for Peace</a> (OAP) did the same, irradiating 413 kilograms (911 lb) of gemstones from 1993 to 2003,<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> until the <a href="/facts/Thailand_Institute_of_Nuclear_Technology/Q0uzKAc4">Thailand Institute of Nuclear Technology</a> was established in 2006 and housed the Gem Irradiation Center to provide the service.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a><a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a> </p> <h2 id="materials-and-results">Materials and results</h2> <table><tbody><tr><th colspan="3">Effects of irradiation onvarious gemstone materials</th></tr><tr><td>Material</td><td>Starting color</td><td>Ending color</td></tr><tr><td><a href="/facts/Amber/wN9dVRdv">Amber</a></td><td>Light yellow</td><td>Orangey red,<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a>orangey yellow<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a></td></tr><tr><td rowspan="3"><a href="/facts/Beryl/Fl7q1Hl9">Beryl</a></td><td>Colorless</td><td>Yellow<a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a></td></tr><tr><td>Blue</td><td>Green<a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a></td></tr><tr><td>Colorlessto pale pink(Maxixe-type)</td><td>Deep blue<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a></td></tr><tr><td><a href="/facts/Diamond/IBUdnd1y">Diamond</a></td><td>Colorless oryellowto brown</td><td>Green to blue<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a></td></tr><tr><td><a href="/facts/Fluorite/y2G7C8zk">Fluorite</a></td><td>Colorless</td><td>Various<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a></td></tr><tr><td><a href="/facts/Pearl/7ombxKgg">Pearl</a></td><td>Light colors</td><td>Brown,<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a>gray to black<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a>or gray-blue<a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a></td></tr><tr><td><a href="/facts/Quartz/4n86tE2G">Quartz</a></td><td>Colorless toyellow orpale green</td><td><a href="/facts/Amethyst/CWCPKKrk">Amethyst</a>,<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a><a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a>brown,<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> rose,<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a>"smoky" (light gray)<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a></td></tr><tr><td><a href="/facts/Sapphire/C11GJAmm">Sapphire</a></td><td>Pink withblue tint</td><td>Tint removed<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a></td></tr><tr><td rowspan="2"><a href="/facts/Topaz/jjgWXsSv">Topaz</a></td><td>Yellowto orange</td><td>Intensify colors<a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a></td></tr><tr><td>Colorlesstopale blue</td><td>Brown,<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a>dark blue,<a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a>green,<a class="footnote-ref" id="fnref:52" href="#fn:52"><sup>52</sup></a>sky blue<a class="footnote-ref" id="fnref:53" href="#fn:53"><sup>53</sup></a></td></tr><tr><td rowspan="3"><a href="/facts/Tourmaline/6nbcGRyu">Tourmaline</a></td><td>Colorlesstopale colors</td><td>Brown,<a class="footnote-ref" id="fnref:54" href="#fn:54"><sup>54</sup></a>green-red (bicolor),<a class="footnote-ref" id="fnref:55" href="#fn:55"><sup>55</sup></a>intense pink,<a class="footnote-ref" id="fnref:56" href="#fn:56"><sup>56</sup></a>pink,<a class="footnote-ref" id="fnref:57" href="#fn:57"><sup>57</sup></a><a class="footnote-ref" id="fnref:58" href="#fn:58"><sup>58</sup></a> red,<a class="footnote-ref" id="fnref:59" href="#fn:59"><sup>59</sup></a>yellowish orange<a class="footnote-ref" id="fnref:60" href="#fn:60"><sup>60</sup></a></td></tr><tr><td>Pink</td><td>Intense pink,<a class="footnote-ref" id="fnref:61" href="#fn:61"><sup>61</sup></a>orangey pink<a class="footnote-ref" id="fnref:62" href="#fn:62"><sup>62</sup></a></td></tr><tr><td>Blue</td><td>Purple<a class="footnote-ref" id="fnref:63" href="#fn:63"><sup>63</sup></a></td></tr><tr><td><a href="/facts/Zircon/84APfbLt">Zircon</a></td><td>Colorless</td><td>Brown to red<a class="footnote-ref" id="fnref:64" href="#fn:64"><sup>64</sup></a></td></tr></tbody></table> <p>The most commonly irradiated gemstone is <a href="/facts/Topaz/jjgWXsSv">topaz</a>, which usually becomes blue after the process.<a class="footnote-ref" id="fnref:65" href="#fn:65"><sup>65</sup></a> Intensely blue topaz does not exist in nature and is caused by artificial irradiation.<a class="footnote-ref" id="fnref:66" href="#fn:66"><sup>66</sup></a> According to the American Gem Trade Association, approximately 30 million <a href="/facts/Carat_(unit)/d2jIjtSs">carats</a> (6,000 kg or 13,000 lb) of topaz are irradiated every year globally, 40 percent of which were done in the United States as of 1988.<a class="footnote-ref" id="fnref:67" href="#fn:67"><sup>67</sup></a> Dark-blue varieties of topaz, including American Super Blue and London Blue, are caused by neutron bombardment,<a class="footnote-ref" id="fnref:68" href="#fn:68"><sup>68</sup></a> while lighter sky-blue ones are often caused by electron bombardment.<a class="footnote-ref" id="fnref:69" href="#fn:69"><sup>69</sup></a> Swiss Blue, subtly lighter than the US variety, is caused by a combination of the two methods.<a class="footnote-ref" id="fnref:70" href="#fn:70"><sup>70</sup></a> </p><p>Diamonds are mainly irradiated to become blue-green or green, although other colors are possible.<a class="footnote-ref" id="fnref:71" href="#fn:71"><sup>71</sup></a> When light-to-medium-yellow diamonds are treated with gamma rays they may become green; with a high-energy electron beam, blue.<a class="footnote-ref" id="fnref:72" href="#fn:72"><sup>72</sup></a> The difference in results may be caused by local heating of the stones, which occurs when the latter method is used.<a class="footnote-ref" id="fnref:73" href="#fn:73"><sup>73</sup></a> </p><p>Colorless <a href="/facts/Beryl/Fl7q1Hl9">beryls</a>, also called goshenite, become pure yellow when irradiated, which are called golden beryl or heliodor.<a class="footnote-ref" id="fnref:74" href="#fn:74"><sup>74</sup></a> <a href="/facts/Quartz/4n86tE2G">Quartz</a> crystals turn "smoky" or light gray upon irradiation if they contain an <a href="/facts/Aluminum/7wmR8jYE">aluminum</a> impurity, or <a href="/facts/Amethyst/CWCPKKrk">amethyst</a> if small amounts of iron are present in them; either of the results can be obtained from natural radiation as well.<a class="footnote-ref" id="fnref:75" href="#fn:75"><sup>75</sup></a> </p><p><a href="/facts/Pearl/7ombxKgg">Pearls</a> are irradiated to produce gray blue or gray-to-black colors.<a class="footnote-ref" id="fnref:76" href="#fn:76"><sup>76</sup></a> Methods of using a cobalt-60 gamma ray facility to darken white <a href="/facts/Pinctada_fucata/rcBgRgVw">Akoya pearls</a> were patented in the early-1960s.<a class="footnote-ref" id="fnref:77" href="#fn:77"><sup>77</sup></a> But the gamma ray treatment does not alter the color of the pearl's <a href="/facts/Nacre/a5ek6xm4">nacre</a>, therefore is not effective if the pearl has a thick or non-transparent nacre.<a class="footnote-ref" id="fnref:78" href="#fn:78"><sup>78</sup></a> Most black pearls available in markets prior to the late-1970s had been either irradiated or dyed.<a class="footnote-ref" id="fnref:79" href="#fn:79"><sup>79</sup></a> </p> <h3>Uniformity of coloration</h3> <p>Gemstones that have been subjected to artificial irradiation generally show no visible evidence of the process,<a class="footnote-ref" id="fnref:80" href="#fn:80"><sup>80</sup></a> although some diamonds irradiated in an <a href="/facts/Electron_beam/9jRXSquS">electron beam</a> may show color concentrations around the <a href="/facts/Culet/N6eJCEns">culet</a> or along the keel line.<a class="footnote-ref" id="fnref:81" href="#fn:81"><sup>81</sup></a> </p> <h3>Color stability</h3> <p>In some cases, the new colors induced by artificial irradiation may fade rapidly when exposed to light or gentle heat, so some laboratories submit them to a "fade test" to determine color stability.<a class="footnote-ref" id="fnref:82" href="#fn:82"><sup>82</sup></a> Sometimes colorless or pink beryls become deep blue upon irradiation, which are called Maxixe-type beryl. However, the color easily fades when exposed to heat or light, so it has no practical jewelry application.<a class="footnote-ref" id="fnref:83" href="#fn:83"><sup>83</sup></a> </p> <h2 id="notes">Notes</h2> <h3>Citations</h3> <h3>Works cited</h3> <ul><li>Ashbaugh III, Charles E. (Winter 1988), <a href="https://www.gia.edu/gems-gemology/winter-1988-irradiation-radioactivity-ashbaugh">"Gemstone Irradiation and Radioactivity"</a>, <i><a href="/facts/Gems_%2526_Gemology/JledvKI7">Gems & Gemology</a></i>, vol. 24, no. 4, Gemological Institute of America, pp. 196–213, <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/1988GemG...24..196A">1988GemG...24..196A</a>, <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.5741%2FGEMS.24.4.196">10.5741/GEMS.24.4.196</a>, <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/0016-626X">0016-626X</a>, <a href="https://web.archive.org/web/20081119153902/http://lgdl.gia.edu/pdfs/ashbaughw88.pdf">archived</a> (PDF) from the original on November 19, 2008, retrieved March 11, 2025</li> <li>Crowningshield, Robert (Winter 1981), <a href="https://www.gia.edu/doc/Irradiated-Topaz-and-Radioactivity.pdf">"Irradiated Topaz and Radioactivity"</a> (PDF), <i><a href="/facts/Gems_%2526_Gemology/JledvKI7">Gems & Gemology</a></i>, vol. 17, no. 4, Gemological Institute of America, pp. 215–217, <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/1981GemG...17..215C">1981GemG...17..215C</a>, <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.5741%2FGEMS.17.4.215">10.5741/GEMS.17.4.215</a>, <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/0016-626X">0016-626X</a>, <a href="https://web.archive.org/web/20221018064143/https://www.gia.edu/doc/Irradiated-Topaz-and-Radioactivity.pdf">archived</a> (PDF) from the original on October 18, 2022, retrieved November 13, 2022</li> <li><a href="/facts/Jackson_School_of_Geosciences/Fh9tAeJx">Department of Geological Sciences</a> (1998), <a href="https://www.geo.utexas.edu/courses/347k/redesign/Gem_Notes/Pearl/pearl_main.htm"><i>Pearl</i></a>, <a href="/facts/University_of_Texas_at_Austin/6NApstxT">University of Texas at Austin</a>, <a href="https://web.archive.org/web/20210616094848/http://www.geo.utexas.edu/courses/347k/redesign/Gem_Notes/Pearl/pearl_main.htm">archived</a> from the original on June 16, 2021, retrieved November 12, 2022</li> <li>Fielding, P. E. (March 1970), <a href="http://www.minsocam.org/ammin/AM55/AM55_428.pdf">"The distribution of uranium, rare earths and color centers in a crystal of natural zircon"</a> (PDF), <i><a href="/facts/American_Mineralogist/y8CVqDB8">American Mineralogist</a></i>, vol. 55, no. 3–4, pp. 428–440, <a href="https://web.archive.org/web/20220506190932/http://www.minsocam.org/ammin/AM55/AM55_428.pdf">archived</a> (PDF) from the original on May 6, 2022, retrieved November 21, 2022</li> <li>Hurlbut, Cornelius S.; Kammerling, Robert C. (1991), <a href="https://web.archive.org/web/20250109044222/https://batch.libretexts.org/print/Letter/Finished/geo-3164/Full.pdf"><i>Gemology</i></a> (PDF), <a href="/facts/Wiley-Interscience/53g3LqJc">Wiley-Interscience</a>, <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 0-471-52667-3, archived from <a href="https://batch.libretexts.org/print/Letter/Finished/geo-3164/Full.pdf">the original</a> (PDF) on January 9, 2025, retrieved November 4, 2022 – via <a href="/facts/LibreTexts/8ackRcD8">LibreTexts</a>.</li> <li>Jewelers Circular Keystone, ed. (December 1990), <a href="https://link.gale.com/apps/doc/A9243796/ITOF">"NRC Cracks Down on Irradiated Topaz"</a>, <i>Jewelers Circular Keystone</i>, vol. 161, no. 12, Reed Business Information, Inc. (US), p. 39, <a href="/facts/ISSN_(identifier)/DPAflDvU">ISSN</a> <a href="https://search.worldcat.org/issn/1534-2719">1534-2719</a>, <a href="https://web.archive.org/web/20221113195751/https://go.gale.com/ps/i.do?p=ITOF&u=wikipedia&id=GALE%7CA9243796&v=2.1&it=r&sid=ebsco&asid=750bad00">archived</a> from the original on November 13, 2022, retrieved March 11, 2025 – via <a href="/facts/Gale_OneFile/kKSW05y4">Gale OneFile</a></li> <li>Journal of Physics: Conference Series, ed. 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