AGTA GTC's Laboratory Update for November 29, 2005
In this message…
The Synthetic Healing of Ruby
One of the least understood treatments applied to any gemstone is that of the flux healing of rubies. Often mislabeled as, and confused with, “glass-filling,” in fact the treatment involves the use of fluxes to “heal” open fractures in ruby. Today, despite the fact that the process has been discussed at dozens of meetings, most jewelers are completely unaware of the treatment method and its impact on a gemstone. The following is designed to shine light into this misunderstood industry corner.
Figure
1. Anatomy of a
healed fracture |
The flux healing process
Flux healing involves heating corundums with borax or other fluxes. These fluxes actually dissolve the surfaces, including the internal surfaces of cracks. The corundum within this molten material then redeposits on the fracture surfaces, filling and healing the fractures shut. Undigested material cools into pockets of flux glass. Essentially this amounts to a microscopic deposition of synthetic corundum to heal the cracks closed. This treatment is applied to virtually all rubies from Burma’s Mong Hsu mines, which have produced the lion’s share of facet-grade ruby over the past 15 years.
Figure 2. Diagram of a flux-healed fracture The mechanism of flux healing of a fracture in corundum. A. Open
fracture/fissure,
unhealed. |
Figure 3. Flux-healed fracture Moderate magnification reveals a flux-healed fracture in a Mong Hsu ruby from Burma. The irregular dark areas are pockets of residual flux, while the red areas in between are where the once open fracture has healed shut with microscopic amounts of what is essentially synthetic corundum. Photo © R.W. Hughes |
In the broadest sense, this is akin to the oiling of emerald – both treatments involve reduction of internal reflections from cracks/fissures. Similar to placing an ice cube in water, a filled fracture is much less visible because the filler replaces air (refractive index = 1.00) with a substance that has a refractive index that more closely matches the gemstone itself (1.76–1.77). However, the flux healing of Mong Hsu rubies differs in three important respects:
- The Mong Hsu ruby treatment is not a fracture filling, but a permanent healing or regrowth of the fractures and fissures, with any residue merely a remnant of the process. In many respects, it is a welding of fractures, similar to the joining of two pieces of metal with heat and a flux to fuse them together.
- The treatment is permanent and irreversible. Unlike the oil in an oiled emerald, flux remnants will not drain out in the future, nor can they be removed. There is no way to return a gemstone to the untreated state.
- The treatment actually improves a gemstone’s durability, since the fractures are permanently welded shut.
In the past, some have argued that the flux remnants are an accidental byproduct of what amounts to "normal" heating. Nothing could be further from the truth. While Mong Hsu rubies are heated for two different reasons (to remove the blue color and heal the fractures), the flux is used solely to heal fractures. This is why fluxes are generally not used when heating clean gemstones (such as pink sapphires from Madagascar) to remove similar blue overtones.
Summary
From the above, it should be clear that the flux-healing treatment is entirely different from both ordinary heat treatments, as well as fracture-filling treatments. If lumped together with simple heat treatment, it will completely redraw the map, not just for ruby, but also potentially for the entire gemstone industry. Treatments such as this underscore the need for widespread educational programs, along with modern laboratories, such as the AGTA GTC.
Figure 4. Surface view of a flux-healed fracture A highly magnified photo showing a single facet’s surface in reflected light where a fracture breaks the surface in a flux-healed Mong Hsu ruby. The dotted red line shows the path of what was once an open fracture, displaced slightly to the right so you can see surface detail. The irregular black areas are surface cavities where bubbles in the flux were cut through, while the irregular gray areas are residual flux glass that has been polished. Note the lower luster compared with the surrounding corundum. In between the surface cavities and flux glass are healed areas, indistinguishable from the surrounding corundum. Photo © R.W. Hughes |
• • • • •
Note: Abstracted from Fluxed Up: The Fracture Healing of Ruby by Richard W. Hughes (with John Emmett). That article was awarded the 2005 Richard T. Liddicoat Journalism Award by the American Gem Society.
Give the Gift of Peace of Mind with an AGTA GTC Report
It is no secret that technological advances have led to an explosion of ever more sophisticated synthetic and treated gemstones. Consumers have a broad range of purchase possibilities and if they lack confidence in our jewelry and gemstone products, they will look elsewhere.
One of the best ways to inspire consumer confidence at the point-of-sale is to present gemstones with an AGTA Gemological Testing Center Identification or Origin Report. These attractive reports can be the difference between the choice of a fine gemstone gift, or some other product.
We would remind our customers that with the holiday gift-giving season rapidly approaching, the demand for our gemstone-testing services will also increase. Beat the rush and submit your gemstones now. This will ensure that you have professional reports at the ready when it comes time to close a sale.
The AGTA Gemological Testing Center Identification Report provides a perfect point-of-sale tool for consumer peace of mind. |
AGTA GTC on the Web
A number of clients have asked us to consider making our gemological bulletins available to a wider audience. Towards that aim, over the past few months we have built a website specifically for the AGTA Gemological Testing Center. It is now live and offers a complete archive of our e-mail bulletins, along with a full description of the lab and its services.
See it at www.agta-gtc.org or link from AGTA’s regular site, www.agta.org.
The new AGTA GTC website offers the most up-to-the-minute gemological news, along with a full description of the lab and its services. |
