Professional Jeweler Archive: Postal Service Irradiation Process May Affect Some Gems

February 2002

Gemstones & Pearls/Gemology

Postal Service Irradiation Process May Affect Some Gems

The solution to killing anthrax spores raises a problem when shipping gemstones through the mail

United States. Recently, however, incidences of binfection by anthrax spores sent through the mail have 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 kills anthrax spores (as well as other biological agents) in the mail as it is being processed.

One company with which the Postal Service contracted, SureBeam (a subsidiary of Titan Corp.), provides a type of linear accelerator that creates a beam of high-energy electrons. In effect, this equipment uses irradiation to kill the anthrax spores.

However, we know this type of irradiation is often used intentionally to change the color of some gems – and could produce an undesirable result as well. Recognizing the potential impact of this development on the jewelry industry and the consuming public, GIA decided to test the effect of the proposed postal irradiation process on various gems.

The Process

A spokesman for SureBeam told us the actual dosage the Postal Service uses is 56 kilograys (equivalent to 5.6 megarads). This figure was 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 used by the USPS.

For these initial tests, we chose gem materials we know to be affected significantly by irradiation. This group consisted of two types of cultured pearls plus eight gem species (diamond, kunzite, morganite, quartz, sapphire, topaz, tourmaline and zircon – all natural) and a number of varieties of those species for a base of 16 samples. We also added to this group a 14k 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 packaged in the same manner we use routinely to ship gems from the GIA Gem Trade Laboratory. Because stones are often shipped more than once (sent out on memo, returned or sent to a manufacturer for mounting and then sent back, etc.), 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, with just one exception: Because we had only one sample of a heavily included gray diamond, we placed this in the package that was to receive four scans to confirm it would not retain 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 the individual gemstones for any 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 exhibited a dramatic change in color, as described in the table below.

Before and after images of the sapphires and citrines illustrate some of the significant changes we observed (see examples on these two pages).

For most of the samples we examined, 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 the three samples of colorless quartz: The one in the box scanned once came out 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 gem material we examined, there was no visible difference related to the number of scans.

Implications for the Future

We understand the Postal Service is scanning only a small portion of the mail – and only letters and flat envelopes. “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,” says John Dunlap, manager of materials handling and deployment for the USPS Engineering Group, which oversees mail sanitization operations. Other postal authorities have commented 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 FedEx. They all said they don’t use irradiation procedures and don’t plan to start at this time. Nevertheless, it is important the trade and the consuming public be aware that some gem materials could be affected by the sanitization process, and every effort should be made to ship such materials by methods that are not likely to be exposed to the procedure.

Note, too, that some of the color changes in our samples are not 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.

Of course, many other gem materials 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. For example, according to Dr. George Rossman of the California Institute of Technology, it is less likely that blue sapphires from basaltic deposits such as Thailand or Australia will change.

We also recognize that some gem material, including ruby and emerald, may be less affected by this radiation dosage.

In the second phase of our testing, which is already under way, we hope to answer these and many more questions about this newest concern to the industry.

By Shane F. McClure, Thomas M. Moses and John I. Koivula
GIA Gem Trade Laboratory

Sapphires before being subjected to the irradiation process used to kill anthrax spores in mailed pieces.
The same sapphires after undergoing the procedure.

Citrines before the procedure.
The same citrines after the procedure.

Copyright © 2002 by Bond Communications