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IRRADIATED TOPAZ and RADIOACTIVITY by Robert Crowningshield

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IRRADIATED TOPAZ and RADIOACTIVITY by Robert Crowningshield NOTES AND* NEW TECHNIQUES IRRADIATED TOPAZ AND RADIOACTIVITY By Robert Crowningshield A parcel of 100 stones of deep blue irradiated topaz, Dr. M. Welt of Radiation Technology, Rock- imported from Brazil, was found to be radioactive at away Township, NJ, was shown a parcel of about a level somewhat higher than typical background 100 unusually deep blue topaz gemstones that activity. Analysis indicates that the material had had recently been imported from Brazil. Upon been treated by neutrons in a nuclear reactor. Most testing, he found them to be radioactive. Two of irradiated topaz in the trade is not radioactive. these stones were further examined by the author Nevertheless, routine testing for radioactivity in and Dr. K. Nassau of Bernardsville, NJ, and are topaz, beryl, green diamonds, red tourmaline, and possibly all gemstones may be advisable for the described below. Subsequently, Dr. Welt tested protection of the jeweler. lighter blue topaz that also proved to be radioac- tive. Representative samples of light and dark ir- radiated stones and a larger, even lighter natural blue topaz are shown in figure 1. Large quantities of colorless topaz are currently being treated by gamma irradiation to turn them EXAMINATION blue, a process that does not produce radioactivity The two stones, 8 cts. and 10 cts. in size, were in the stone (Nassau, 1980). The resulting color exceptionally dark, fine-quality blue topaz. Gem- is a medium deep blue that is significantly darker ological testing revealed a typical natural topaz: than that of most natural blue topaz. A consid- with two-phase inclusions typical of topaz, re- erably darker color does result in rare instances fractive index of 1.61- 1.62, birefringence about (M. Welt, personal communication, 1981); this 0.009, biaxial-doubly refractive, specific gravity blue color is produced by a treatment [nature un- of 3.57, no features observed in the spectroscope, known) that is purportedly used on colorless to- and greenish fluorescence (long-wave, very faint; paz that will not turn blue with gamma rays (M. short-wave, barely detectable). Welt, personal communication, 1981). The 10-ct. stone showed about 0.2 milliroent- gens per hour [rnr/hr)*when tested in contact ABOUT THE AUTHOR with a Geiger counter survey meter, while the Mr. Crowningshield is Vice President-Director of the Gem parcel of about 100 stones shown to Dr. Welt Identification Department of the Gem Trade Laboratory, Inc., New York. - - Acknowledgments: The author wishes to thank Dr. K. Nassau "The Roentgen, rod, rem, and rep are units used for and Dr. M. Welt for experimental results and helpful radiation dose and differ only slightly in value. discussions. Microcuries (pc) are units that measure the quantity '1982 Gemological Institute of America of radioactive material. Notes and New Techniques GEMS & GEMOLOGY Winter 1981 215 Figure 1. Three representative samples of I blue topaz. The two smaller stones on the left have both been irradiated to enhance color. The larger, lighter blue stone on the right has not been treated. 1 Photograph by Tino Hammid. measured at 12 mrlhr. Gamma-ray spectroscopic about for some weeks. It is also evident that the examination (K. Nassau, personal observation, stones were imported without the required radio- 1981) showed the presence of the following active materials import license (issued by the amounts of radioactive elements: Nuclear Regulatory Agency), Second, a spokesperson for the Nuclear Reg- scandium-46: 0.1 pcuries (half-life 84 days) ulatory Agency stated that, for relatively low lev- tantalum-182: 0.002 pcuries (115 days) els of activity such as might be associated with manganese-54: 0.002 pcuries (303 days) a single stone, there are no appropriate standards. iron-59: 0.001 pcuries (45 days) This person added, however, the personal obser- These radioactive elements were probably pro- vation that the 0.2 mrlhr intensity of the 10-ct. duced from neutron exposure in a nuclear reactor stone definitely would be "not desirable" for ex- by neutron reactions with scandium, tantalum, tended personal wear. iron, and cobalt, respectively. It should be noted Third, a survey conducted by Dr. M. Welt, Dr. that the radioactivity from the major emitter, K. Nassau, Mr. S. Church (of Church &Company, scandium-46, is quite penetrating, consisting of Bloomfield, NJ), and others of a wide variety of gamma rays with the relatively high energy of blue topaz, including several lots of the dark blue 889,000 and 1,120,000 electron volts. material, indicates that none of these others con- tained detectable radioactivity above the usual background reading of 0.02-0.05 mrlhr. Accord- DISCUSSION ingly, it is not at present possible to determine A number of important points arise from these the extent of the problem. findings. Fourth, radioactivity has been reported in a First, the nature of the radioactivity indicates number of other gemstones, such as some of the that the stones were exposed to neutrons in a nu- Maxixe-type blue beryls (Nassau, 1973) and the clear reactor. The importer stated that he had ob- occasional old radium-exposed green diamonds tained several hundred of these stones some (Liddicoat, 1981).Testing in the Gem Trade Lab- months previously in Brazil. Given the half-lives oratory has shown that some of the latter are ex- of the radioactive elements involved, it is obvious tremely high in radiation emission, darkening that the stones had been even more radioactive photographic film in just a few minutes. In ad- then; the dealer may have received an undesirable dition, people are experimenting with irradiation dose of radioactivity himself while carrying them on a wide variety of gem materials, for example, Notes and New Techniques GEMS & GEMOLOGY Winter 1981 to turn pale tourmaline dark red (Nassau, 1974). type of gemstone) may wish to obtain a Geiger Tests show that some of these materials may also counter survey meter and check all parcels of be radioactive. It should be noted that even if the stones. A similar test should probably be per- color fades or is removed by heat treatment, the formed routinely on all stones examined in test- radioactivity still remains. ing laboratories. The specific type and intensity of the radio- activity will depend on impurities present in the gemstone as well as on the time of exposure in REFERENCES the nuclear reactor. All radioactive material slowly Liddicoat R.T. Jr. (1981) Handbook of Gem Identification, loses its activity, the time being dependent on the 1 lth ed. Gemological Institute of America, Los Angeles. Nassau K. (1973) The nature of the new Maxixe-type beryl. half-lives of the active elements involved. Lapidary Journal, Vol. 27, pp. 1032- 1038, 1052- 1059. Fifth, for the protection of his staff and himself Nassau K. (1974) The effect of gamma rays on tourmaline, personally, as well as for liability protection with greenish-yellow quartz, pearls, kunzite, and jade. Lapidary Jownal, Vol. 28, pp. 1064-1074, 1084. respect to hiscustomers, the jeweler (particularly Nassau K. (1980) Irradiation-induced color in gemstones. Gems one who handles large parcels of any particular eJ Gemology, Vol. 13, pp. 343-355. NONFADING MAXIXE-TYPE BERYL? By K. Nassau and B. E. Prescott It is sometimes stated that there exists some terial was closely related to, but not identical Maxixe-type deep blue beryl (occasionally misnamed with, the naturally occurring deep blue beryl found "aquamarine") that does not fade. All specimens in 1917 in the Maxixe mine in the Piaui area of ever reported in the literature did fade, typically northeastern Minas Gerais, Brazil, which also to almost colorless in one to two weeks in bright faded. The new material was designated "Maxixe- sunlight or over a somewhat longer period under less type beryl" to distinguish it from the original, intense illumination. A "nonfading" specimen re- cently examined proved to be typical fading Maxixe- natural "Maxixe beryl." Although the stones ap- type beryl. A possible reason why such a stone might pear to fade at the same rate, the color centers in give the impression that it is nonfading is discussed. these two materials have been shown to be slightly With the exception of some brown topaz and some different (Anderson, 19 79). k~~nzte,no significant gemstone material fades on Statements are occasionally made that spe- the same time scale as does Maxixe-type beryl. cific specimens of Maxixe-type beryl do not fade. All such material studied in detail and reported in the literature has been found to fade (e.g., Nas- sau and Wood, 1973a and 1973b; Crowningshield, 1973; Schmetzer et al., 1974; Nassau et al., 1976; Several years ago there appeared on the gemology and Anderson, 1979). One such purportedly non- scene a deep blue beryl that had unusual proper- fading specimen recently became available to the ties. Specifically, the material was at first desig- authors; it was examined to establish if it did fade nated aquamarine, but the dichroism of the stone differed from that of aquamarine. It was soon shown that the color faded upon exposure of the material to heat or to light. A detailed study (Nas- ABOUT THE AUTHORS sau and Wood, 1973a and 1973b; Nassau et al., Dr. Nassau and Dr. Prescott are research scientists residing in 1976) demonstrated that an irradiation-induced Bernardsville and Murray Hill, New Jersey, respectively. color center produced the color and that this ma- "7982 Gemological Institute of America Notes and New Techniques GEMS & GEMOLOGY Winter 1981 217 .
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