To our knowledge, the NRC has still notenforced its regulations, and neutron-irradiated bluetopaz continues to be imported and sold in the U.S.However, no blue topaz containing residual radioactivityhas been reported recently in the trade.
Earlieraround 2000Europe faced similar concernsthat irradiated blue topaz exhibiting residualradioactivity had made its way into several differentcountries (Kennedy et al., 2000).
U.S. Postal Service Irradiation.
During the anthraxscare of late 2001, the USPS irradiated envelopes andpackages to kill potential biological agents. Thecompany that the postal service contracted with toperform the test, SureBeam, used a linear acceleratorto create a beam of high-energy electrons. Thepotential impact of this exposure was immediatelyrecognized, since the same ionizing radiation is routinelyused to change the color in several types of gems. McClure et al. (2001) showed alarming evidenceof several gems that had their color changeddramatically after being exposed in SureBeams facilityto the same dosage as was used for the mail. TheUSPS subsequently abandoned these procedures,after determining that the time and money neededto sanitize all mail would be prohibitive.
In the latter part of the decade, anunusual amount of faceted green quartz suddenlyappeared on the world market. Nearly all thesegemswhich originated from Rio Grande do Sul,Brazilbegan as colorless to light yellow quartz thatwas subsequently irradiated to produce the greencolor (Kitawaki, 2006; Schultz-Güttler et al., 2008).Natural green quartz does exist but is extremelyrare, and greened quartz (also known as prasiolite)is produced by heating certain types of amethyst.Irradiated green quartz shows a broad spectralabsorption at 592620 nm, while prasiolite exhibitsa broad band centered at 720 nm. When examinedunder a Chelsea filter with incandescent light, irradiatedgreen quartz appears red and prasiolite appearsgreen (Schultz-Güttler et al., 2008; Henn andSchultz-Güttler, 2009).
In addition to the huge quantities of irradiatedyellow beryl, which remains undetectable, irradiatedyellowish green beryls were seen. Milisenda (2007a)reported absorption lines between 500 and 750 nmfor the ordinary ray, which are also typically seen inartificially irradiated Maxixe-type beryls. Mili -senda (2007b) reported a beryl with Maxixe-typespectra that was offered for sale as a cats-eye scapolitebut proved to be a blue irradiated cats-eye beryl.
Milisenda (2005a) reported on a parcel ofintense green faceted spodumenes from Pakistan,offered for sale in Idar-Oberstein as hiddenite, thatwere artificially irradiated. The stones revealed abroad absorption band centered at 635 nm. Asexpected for this material, the color faded to the originalpale pink within a few days.
The irradiation of pearls has been known fordecades, and little has changed since 2000. The treatmentis almost always associated with freshwaterpearls or nuclei, since the radiation appears to alterthe state of the trace element manganese found inthese materials. Gray, silvery gray, and black colorshave all been produced. In fact, pearls were one of thegems significantly altered by the U.S. postal serviceirradiation mentioned above. Detection remains achallenge in some cases, and research has continuedon its identification (Liping and Zhonghui, 2002).
As it has been for centuries, applying surface coatingsto change the color of gems continues to be acommon practice. Not only do gemologists need tobe aware of high-tech coatings, we must alsoremember to look for older, simpler alterations.Diamonds. Just as Miles (1964) described decadesago, in 2003 Sheby reported seeing two slightly yellowdiamonds that were coated with a blue materialto improve the apparent color. Also as a recentreminder, Eaton-Magaña (2010) described a 1.5 ctdiamond with a color equivalent to Fancy pink thatrevealed a nearly imperceptible trace of reddishmaterial on a natural when viewed with the microscope.After cleaning, the diamond was graded Faintpink.
Sputter-coated optical thin films were originallydeveloped in the 1940s to improve the optical performanceof lenses. We continued to see similar coatingtechnology used on diamonds in the 2000s. Evans etal. (2005) and Wang et al. (2006b) reported on faceteddiamonds that were colored pink by sputter-coatedthin films. A potentially new kind of diamond coatingwas described by Epelboym et al. (2006)ratherthan using the fluoride coatings previously known,pink and orange-treated diamonds were suspected ofbeing coated with a silica film doped with gold.