GIA: U.S. Postal Service irradiation process may affect some gemstones

The Gemological Institute of America (GIA) has issued a gem and jewelry trade alert regarding the irradiation process that is being used by the U.S. Postal Service to sanitize mail containing the anthrax virus. The process, GIA say, may affect the color of some gemstones. Following is the GIA report.

GIA 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 potential 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 standards throughout the gem and jewelry industry. Today’s Special Issue of the GIA Insider presents the first results of this testing.

The jewelry industry relies heavily on the U.S. Postal Service to ship gems and jewelry throughout the United States. As most are aware, the recent incidences of people being infected by anthrax spores 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 the postal service has contracted, SureBeam (a subsidiary of Titan Corp.), makes equipment designed to combat food-borne pathogens such as salmonella. SureBeam provides a type of linear accelerator that creates a beam of high-energy electrons. In effect, they are using irradiation to kill the microorganisms that often contaminate food.

However, we know that this type of ionizing radiation is often used intentionally to change the color of some gem 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 gem materials.

The Process
A spokesman for SureBeam 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 Laura Smith, Quality Assurance 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 tests, we chose gem materials that, based on our many years of experience and discussions with experts in the field, we know to be affected by irradiation in a significant way. This group consisted of two types of cultured pearls plus eight different gem species and a number of varieties of those species – all of which were natural – for a base of 16 different samples, as follows:

Diamond – near colorless
Diamond – gray (due to inclusions)
Cultured Pearl – bead-nucleated saltwater
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

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 structural differences 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 known geographic origin.

We also added to this group a 14 karat yellow gold ring, to reassure 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 significant difference.

The contents of the boxes were identical, except there was only one heavily included gray diamond. We placed this in the package that was to receive four scans to see if it would retain any residual radioactivity, as is often detected in irradiated black diamonds.

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 unopened packages as well as on the individual samples. Fortunately, no residual radiation was detected.

Next, we examined all the individual stones for obvious changes 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.

Before-and-after images of the freshwater cultured pearls, kunzite, and sapphire illustrate some of the significant changes we observed.

(The pearl images along with a chart of how individual stones were affected by the process can be seen at

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 example, 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 the number of scans.

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 Handling 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 currently 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 letters, 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.

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 ed., 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 degrees 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,” 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.