A system that the U.S. Postal Service will use to eliminate the threat of anthrax may produce color changes in gemstones. The technology, an electron-beam system from SureBeam Corp. of San Diego, Calif., “has been used to turn topaz from colorless to blue; to change tourmaline from pale pink to bright red; and to make smoky quartz from colorless quartz,” says Michael Stern, director of technological applications for Titan Scan Technologies, parent company of SureBeam. But Stern feels that the doses used to impart color to gemstones are much higher than doses being considered for anthrax destruction.
Titan is working with federal agencies to install systems that will provide a safe mail stream with respect to biological contaminants. The award of approximately $26 million to SureBeam by the newly established Office of Homeland Security will be used for eight SureBeam systems.
The Gemological Institute of America has been experimenting with SureBeam’s technology to test the stability of color in gemstones that have been subjected to anti-anthrax irradiation. Results show dramatic color changes in pearls, sapphire, quartz, kunzite, and topaz. White cultured pearls change to gray, pale blue sapphires change to a deep orange, and kunzite—which is naturally pink—came through the mail irradiator as a green spodumene. GIA’s results showed “no perceptible color change” in diamond.
Research gemologist Martin Haske of Adamas Gemological Laboratory in Brookline, Mass., also conducted tests on colored stones and diamonds at the TitanScan/SureBeam electron beam irradiation facility in Denver. These tests were sponsored in part by grants from the American Gem Society Laboratory in Las Vegas and David Atlas & Co. of Philadelphia. Haske found some interesting—and contradictory—results.
“We subjected over 100 gemstones to two irradiation runs,” says Haske. (A double run duplicates the typical out-and-back shipment of gems on memo.) “Pearls, fluorites, kunzites, quartzes, CZs, and zircons showed dramatic changes in visual appearance.”
Haske’s diamond samples showed no dramatic changes in color appearance, but his SAS2000 room-temperature spectroscopy unit showed a small loss in transparency, typically associated with GR1 radiation damage.
“The sample [shown on p. 40] clearly indicates this apparent transmittance shift at about 741 nm,” notes Haske. “This same type of signature—a slope change at 741nm, and resultant transmittance loss—although more drastic, can be seen in [heavily] irradiated [and annealed] fancy yellow diamonds.”
Haske believes that these data contradict GIA’s findings, and that borderline colors may be the ones to show a visible change. Colorless CZ changes to yellow; fluorite, multicolor banded, turns black; and zircon changes from colorless to brown.
According to Shane McClure, director of West Coast Identification Services for GIA’s GemTrade Lab, the U.S. Postal Service is using this technology only on flat envelopes—so far. But he advises jewelers to avoid any possible irradiation of their gemstones and find alternatives to using the Postal Service. That said, according to researchers, this might not be a big issue for the industry, since registered mail—which has a paper trail to the sender—may not be irradiated.
Problems other than gemstone enhancement also could affect jewelers’ use of the mail. “Electron-beam irradiation will, in fact, expose unprocessed photographic film in a similar manner as sunlight,” says McClure. “However, unlike sunlight, highly energetic electrons have the ability to penetrate even opaque packaging materials and affect their contents. Developed negatives are likely to show coloration, typically of the yellow/orange/brown variety, upon irradiation. Polycarbonate-based materials, including some eyeglass lenses, will develop [similar] coloration.”
A communication from SureBeam also notes that “controlled applications of low-dose electron-beam irradiation will erase the data on magnetic data storage media (e.g., floppy disks and videotapes) as well as some credit card magnetic strips.”
McClure noted that gold also was tested to see if any residual radioactivity would be retained by the precious metal. None was noted.
For information about SureBeam, visit www.Surebeam.com. For information on the effects of ionizing radiation on gemstones, visit the Web site of the Fallbrook Gem and Mineral Society at http://fgms.home.att.net/imp-gems.htm. For a detailed report on GIA’s findings, log onto www.gia.edu/gandg/special-issue-112701.cfm.