The Gemological Institute of America constantly strives to remain on top of issues that can affect the gem and jewelry industry and the public. When we became aware of the U.S. Postal Service's proposed "sanitization" of mail using ionizing radiation,we immediately began investigating the potentail impact of this process on gems shipped through the USPS.Such laboratory research is part of GIA's ongoing commitment to protecting the public interest and maintaining high professional standard throughout the gem and jewelry industry.
           The jewelry industry relies heavily on the U.S. Postal Service to ship gems and jewelry throughout the USA. At most are aware , the recent incidences of people being infected by anthrax apores sent through the mail has caused the USPS to seek ways to protect postal employees and the public from this potential threat. One part of this effort is to use a technique that actually kills anthrax spores (and other biological agents ) in the mail as it is being processed.

           One company with which postal service has contracted,SurBeam (a subsidiary of Titan corp.), makes equipment designed to combat food-borne pathogens such as salmonella. SurBeam provides a type of linear accelerator that creates a beam of high-energy electrons. In effect , they are using irradiation to kill the microorganism that often contaminate food.

           However, we know that this type of ionizing radiation is often used intentionally to change the color of some materials -- and could produce an undesirable result as well. We at GIA and others in the trade immediately recognized the potential impact of this development on the jewelry industry and the consuming public , so we decided to test the effect of the proposed postal irradiation process on the gem materials.

Freshwater cultured pearls before (top) and after (bottom) irradiation by current postal sanitization procedures.
           A spokesman for SurBeam told us that the actual dosage being used by the postal system is 56 kilograys,which is equivalent to 5.6 megarads. This figure was later confirmed by Luara Smith,Quality Assuran ce Manager for Titan Scan Technologies, another Titan corp. subsidiary,who agreed to run tests for us under the same conditions that are being used by the post office.

           For these initial test , we chose gem materials that , based on our many years of experience and discussions with expert in the feild, we know to be affected by irradiation in a sinificant way . This group consisted of two types of cultuered pearls plus eight different gem species and a number of varieties of those species--all of which were natural -- for a base of different samples, as follows:
  Diamond - near colorless  
           Of course,there are many other gem materials that might be affected by this process,and the same gem materials from different localities or with chemical or structeral differrences might not respond the same as our samples. We intend to follow up this initial study with one that will encompass many other species as well as stones of know geographic origin. We also added to this group a 14 karat yellow gold ring ,to ressure the industry that gold jewelry would not retain any residual radioactivity from this process.
           We made up three sets of these samples and placed them in boxes that were packaged in the same manner that we routinely use to ship gems from the GIA Gem Trade Laboratory. Because stones are often shipped through the mail more than once(e.g., sent out on memo,returned or sent to a manufacturer for mounting, and then sent back or on to someone else), we asked to have one package scanned just once, another scanned twice, and the third scanned four times -- to see if the cumulative effect of multiple scans caused any sinificant difference.
           The content of the boxes were identical,except there was only one heavily included gray diamond. We placed yhis in the package that was to receive four scans to see if it would retain any residual radioactivity, as is often detected in irradiation black diamonds.
  Diamond - Gray (due to inclusions)  
  Cultured Pearl - bead-nucleated freshwater  
  Cultured Pearl - tissue-nucleated freshwater  
  Quartz - colorless  
  Quartz - yellow (citrine)  
  Sapphire - light blue  
  Topaz - colorless  
  Tourmaline - near colorless  
  Tourmaline - light pink  
  Tourmaline - bi-colored green and pink  
  Zircon - colorless  
  Zircon - yellow  
  Zircon - green  
Left to right : Kunzite before
Kunzite After Irradiation by current postal sanitization procedures.
           After we retrieved the packages, we first checked for the presence of residual radiation with a Victoreen model 290 radiation survey meter. This was done on the upopened packages as well as on the individual samples. Fortunately, no residual radiation was detected.
           Next, we examined all the individual stones for obvious change in appearance. (Changes in spectra and analytical data will be addressed in the course of future research). All of the gem materials other than diamond showed a dramatic change in color,as described below:
  Gem Material Before After  
  Diamond near colorless near colorless, no change  
  Diamond gray gray - no change  
  Kunzite pink green  
  Morganite brownish or orangy pink yellow  
  Cultured Pearl (saltwater) white gray  
  Cultured Pearl (freshwater) white gray  
  Quartz colorless brown  
  Quartz yellow brown  
  Sapphire light blue yellowish orange  
  Topaz colorless brown  
  Tourmaline near colorless light pink  
  Tourmaline light pink darker pink  
  Tourmaline bi-colored green green - no change  
    and pink pink - darker  
  Zircon colorless pinkish brown  
  Zircon yellow yellowish brown  
  Zircon green (greenish)  
      yellowish brown  
           We did not separate out the results for one ,two, or four scans because, for most of the samples, the changes were just as dramatic in the box that went through only one scan as in the box that went through four.However, the degree of change was different for some stones. For examples, the colorless quartz in the box that was scanned once came out a medium brown; a similar sample in the box scanned twice turned dark brown; and the third sample, scanned four times, became almost black. For the other gems, there was no visible difference related to number of scans. GIA has absorption spectra on the three near-colorless diamonds that were irradiated by Titan Scan Technologies using the same process currently being by the USPS to "Sanitize" mail. All three diamonds (which were sawn half octahedrons) are type la; two were assessed as "J" color and the the third, "I". Using a spectronic Unicam model UV-540, UV-VIS spectrophotometer, we ranultraviolet-visible spectra at cryogenic temperatures on these samples both before and after they went through the sanitization process. This was done to document any potential change in the 200-850 nm spectral range, the region where radiation-related absorption features occur in diamond. The spectra showed that all three were typical Cape series diamonds with relatively weak N3 centers (415 nm) and no other relevant features.

           As we expected, given our knownledge of the typical effect on diamonds at radiation dosage used, there were no detectable changes in the spectra. In particular, no radiation-related spectral featured had been added. Also, as indicated in the earlier entry, there was no perceptible change in color (as determined by experienced graders) either.

           Other colors and types of diamonds will be included in GIA's ongoing research into the potential impact of postal irradiation procedures on gem materials.
Implications for the future
           Currently, the U.S. post office is scanning only a small portion of the mail and only letters and flat envelopes. John Dunlap, Manager of Materials Handing and Deployment for the USPS Engineering Group, which oversees mail sanitization operations, told us that "Probably nothing will be done to packages that are sent registered or certified [the preferred method for the jewelry industry], since we now require information from the sender." Other postal authorities have commented that the cost and time required to scan all mail would be prohibitive.

           We also contacted the U.S. Customs Service, Brinks, Malca Amit, UPS, and Federal Express to see if they were curretly using sanitization procedures or had plans to do so. They all stated that no irradiation procedures were being used or were planned at this time. They all have imposed stricter limitations with letter, and some of the shippers are no longer transporting envelopes. Nevertheless, it is important that members of the trade and the consuming public alike be aware that some gem materials could be affected by the procedure, and every effort should be made to ship such materials by methods that are not likely to be exposed to the sanitization process.
Sapphire before (top) and after (bottom) irradiation by current postal sanitization procedures.

 Note, too, that some of the color changes seen in our samples would not be permanent. Some of these colors will fade with exposure to light back to their original colors.

           Others can be changed back with heat. Still others will never revert to their original color. (For more on the color stability of irradiated gems, see K Nassau, "Gemstone Enhancement," 2nd edition, Butterworth-Heinemann, OXford, 1994).

           Also as mentioned above, not all members of the same species or even the same variety will react similarly. For example, according to Dr George Rossman of the California Institute of Technology, it is likely that darker blue sapphires and almost certainly those from basaltic deposits such as Thailand or Australia-will not change at all.

           We recognize that other gem species or varieties, including ruby and emerald, may be affected to lesser degress by this radiation dosage. In the second phase of our testing, which is already underway, we hope to answer this and many more questions about this newest concern to the industry.

           For background information on commercial irradiation of gem materials, see C E Ashbaugh, "Gemstone Irradiation and Radioactivity," in "Gems & Gemology," Winter 1988, pp. 196-213. For more on the possible effects of postal sanitization on gem materials, see the upcoming Winter 2001 issue of "Gems & Gemology."


Web Counter