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Year 4 Issue 6 July 2005
GIA gem laboratory uploads industry on syntheticrubies with...
Seeing in the Dark, UV luFluorescence as a gem dealer's tool
 
 
 
       
  GIA gem laboratory updates industry on synthetic rubies with Healed Fractures and the durability of lead-glass fillings in rubies  
 
   As a prelude to the gem and jewelry shows in Las Vegas, the Gemological Institute of America (GIA) wanted to inform the industry of two important developments in the colored stone industry.
   The first involves the recent appearance of nu­merous examples of synthetic ruby that have been altered to look like heat-treated natural rubies. These synthetics, which reportedly originate in Thailand, have been circulat­ing in the New York trade for the past few weeks.
   The second involves an update on the clarity enhancement of rubies with a lead-glass filler, which was first described in 2004. As part of GIA's ongoing research, the GIA Gem Laboratory has been conducting a study on the durability of these fillers under various conditions. Preliminary results were also reported in a June 1 Special Issue of the GIA Insider.
  
 

Synthetic Rubies with flux-induced healed fractures that are represented to be heat-treated natural rubies
 
 
   The GIA Gem Laboratory has recently seen an" increase in the number of synthetic rubies with flux-induced healed fractures that are being offered as heat-treated natural rubies in the market. During the past few weeks, the GIA Gem Laboratory has examined more than 20 such synthetic rubies, ranging from approximately 3 to 25 carats, which were melt-grown by the Verneuil technique (figure 1).

   These synthetic stones had been guench-crackled and subsequently heated with fluxing agents to induce healing along the fractures, thus mimicking the healed fractures commonly seen in natural rubies that have been heat treated. Most of the suppliers indicated that these synthetics were coming from Bangkok, and that they were being represented as heat-treated natural rubies.
  
 
 
 
Figure 1. These three synthetics (4.45-7.16 cts.) are typical of the flame-fusion synthetic rubies with flux-induced healed fractures that are being offered for sale as heat-treated natural rubies. These three stones were part of a parcel, all of which were the same material, that had recently arrived from the trade in Bangkok, Thailand. Photo by Jessica Arditi.

Figure 2. The network of flux-induced healed fractures in these melt-grown synthetic rubies revealed a typical "chicken-wire" pattern that occurs when such a stone is quench-crackled and then heated with fluxing agents to induce healing. Photomicrograph by Christopher P. Smith; magnified 16x.

Figure 3. Careful examination of these synthetics with a standard jeweler's loupe or microscope revealed subtle-to-distinct curved strait, which are typical of rubies grown by the Verneuil technique. Photomicrograph by Christopher P. Smith; magni-fied 16x.

Figure 4. Many of the samples revealed clusters of tiny gas bubbles. Photomicrograph by Christopher P. Smith; magnified 38x.
 
 
   These synthetic rubies can be identified by careful examination with a loupe or microscope. All of the samples GIA examined revealed a typical pattern to the network of healed fractures (figure 2) and fine curved strait (figure 3). In many cases, tiny gas bubbles were also seen (figure 4). Synthetic rubies such as these have been encountered sporadically over the last two decades (see, e.g., J. I. Koivula, "Induced Fingerprints," Gems & Gemology, Vol. 19, No. 4, 1983, pp. 220-227); however, the number of samples examined by the GIA Gem Laboratory in the past few weeks represents a dramatic increase from those seen in the past.

  
  Update on the durability testing of lead-glass-filled natural rubies  
 
   As part of its continuing research on the lead-glass fracture filler in natural rubies (reported in the GIA Insider, Sept. 17, 2004 and in Gems & Gemology, Fall 2004), GIA has been conducting tests to determine the durability of these fillers under a variety of conditions.
   GIA research members acquired more than 30 samples, from the trade in New York and Bangkok that had been treated by various parties in Thailand. They subjected 15 of these samples to a variety of durability tests to determine how the lead-glass filler would hold up under various conditions. Chemical analyses revealed that the fillers in these samples had a similar major-element chemical composition, involving oxides of lead, silica, and alumina.

  
 
   The samples were exposed to a variety of situa­tions that such stones might be expected to experience during jewelry manufacturing (including stone setting, re-tipping of prongs or jewelry repair, re-sizing of rings, filing, polishing, and ultrasonic and steam cleaning). Overall, the lead-glass fillers in these samples did not alter in ap­pearance during these various manufacturing procedures. However, it is very important to note that when the stones were immersed in a pickling solution after the manufacturing processes, to remove any tarnish or other residues from the exposure to an acetylene-oxygen torch, the lead glass was readily etched.
  
 
These two 2-ct. rubies from Madagascar had been clarity enhanced n Thailand
using a high-lead-content glass. Prior to durability testing, these two
stones were a matched pair. The stone on the right was immersed in
caustic soda (NaOH) for one hour. This base solvent readily etched the
lead-glass filler, thereby making the fractures visible once again and
dramatically affecting the transparency of the stone. Photo by Elizabeth
Schrader.
 
 
   Another series of tests involved the durability of the lead-glass fillers when they came in contact with various solvents including acids (such as aqua Regia), base solutions (such as caustic soda), and household products (such as a commercial drain cleaner, ammonia, bleach, and concentrated lemon juice). In virtually all of these instances (with the exception of the ammonia, where little alteration took place), the lead-glass fillers were readily attacked, thus making the fractures much more visible (figure 5). The full details of the characterization of these samples and the results of durability testing will be submitted for publication in an upcoming issue of Gems & Gemology.
  
 
 
 
Figure 6. A blue flash effect easily identifies the presence of a lead-glass filler in this ruby. This feature can be seen with a standard jeweler's loupe or microscope. Photomicrograph by Christopher P. Smith; magnified 18x.

Figure 7. Another common characteristic of the lead-glass filler is the presence of gas bubbles, visible along the fractures. Phot­omicrograph by Christopher P. Smith; magnified 28x.
 
 
   The presence of lead-glass filling in a ruby can be identified by the characteristic blue "flash effect" (figure 6) and gas bubbles (figure 7).
A chemical analysis will also readily determine the presence of lead.
  
   
       Seeing in the Dark, UV FluFluorescence as a gem dealer's tool  
 
   In a previous installment, we looked at the use of UV fluorescence as a simple but powerful tool. Below are a few more examples illustrating how the technique can help in certain identifications.
  
    Figure 1. Fluorescent fillers in emerald
     
   Emeralds are typically treated by filling their fissures with oils/resins. Some of these fluoresce. In the photo above, an emerald is exposed to long-wave UV light. The filler in the fissures is clearly identified by its bluish fluorescence. Note that the body color of the gemstone appears much different under UV light. Photo: Richard W. Hughes/AGTA GTC
   Two different filled emeralds under LW UV light. Photos: Henry Hanni/SSEF

  
 
    Figure 2. Additional examples of fillers in emerald
 
   Similar to blue sapphires and rubies, when some pink sapphires are heat treated, they will display a zoned, chalky fluorescence in short-wave UV light, as shown above.
Figure 3. Pink sapphire    
 
   The author took the photos in these articles using the following crude set-up. Astoneholderwas taped to a gooseneck arm to hold the gemstone in place, A Nikon D70 digital camera with a 60mm macro lens. Also used were two screw-on close-up lenses, to further increase magnification. Photo: Richard Hughes/AGTA GTC
Figure 4. Photographing fluorescence    
     
Meet Our Staff: Dr. Lore Kiefert - Laboratory Director
   Lore Kiefert (born in Heidelberg, Germany) began studying Mineralogy in 1981. In 1987, she obtained her master's degree with a thesis on the distinguishing char­acteristics of Gemmology.

   In April 1994 she joined the SSEF Swiss Gemmo-logical Institute, beginning her distinguished gemological career. Lore joined the SSEF, when the organization was located in Zurich, as Assistant Director. The SSEF moved to Basel in the same year. Lore was awarded her Ph.D. in 1996 and her FGA (Diploma in Gemmology) early in 1998, and was appointed Director of the SSEF Colored Stones Department in 2000.

   Lore is a prolific writer, authoring a large number of scientific and gemoiogical papers. Indeed, the latest issue of the Journal of Gemmology (January/April 2005) alone contains three different papers she co-authored. In addition, Lore has contributed to the Handbook of Raman Spectroscopy and the Handbook of Raman Spectroscopy in Art and Archaeology. She has lectured at numerous scientific and gemological conferences in Australia, South Africa, the United States, England, Belgium, Czech Re­public, Austria, Holland, Germany, and various places in Switzerland.

   Lore brings great expertise both in colored gem-stone identification and origin determination to the GTC.

The AGTA GTC in Las Vegas

   Once again, the AGTA GTC will be participating in The JCK Show - Las Vegas 2005, offering a range of gemological services, such as:
   • Identification reports for all kinds of gems, including the identification of clarity enhancement fillers.
   • Country-of-Origin reports for ruby, sapphire and emerald.
   The AGTA Gemological Testing Center provides the industry and the public with a complete range of serv­ices, including gemstone identification, origin determination and pearl identification. The laboratory, which is located in New York City, is equipped with the latest, technologically advanced, investigative equipment.
   
www.agfa.org