May 10th 2010: GIA Laboratory Bangkok a new study on the heat treatment of rubies from Mozambique is now online on www.giathai.net:

Here is a link to the Mozambique special issue where you can find this study: "FAPFH/GFF Treated Ruby from Mozambique, a preliminary report" by V. Pardieu, N. Sturman, S. Saesaew, G. Du Toit and K. Thirangoon released May 11, 2010.

The ruby deposit in Montepuez was discovered during spring 2009 (see our GIA Mozambique expedition report). Rapidly many rubies from that new location were seen in Bangkok, Thailand. First we saw at GIA Lab Bangkok many unheated rubies but then more and more heated rubies. Unlike rubies from the Niassa deposit that were commonly seen treated using lead glass, these rubies were treated using some flux assisted heat process.

Dont get us wrong: It is not what we can really call a new treatment:

Flux healing using borax and silica is going on for nearly 20 years with rubies from Mong Hsu (Burma) and rubies from other deposits (usually marble type like Vietnam, Afghanistan, Tajikistan, Kenya, Tanzania,...) But the treatment is now performed also on rubies from the new deposit in Montepuez, Mozambique (which is not a marble type deposit). Usually what lab gemologists used to see with flux healed Mong Hsu rubies where healed fissures and sometimes glass filled cavities, but most of the time the stones were cleaned with acid before to be send to the lab and thus there was no glass filled cavities.
The new thing is that most of the flux heated rubies from Mozambique which were submitted to the GIA labs recently in Carlsbad, New York and Bangkok were obviously not cleaned with acid and has some large fissures filled with glass or partially healed and partially filled with glass (as the healing was obviouly far to be complete):

"Glass filled and healed fissure in Mozambique ruby"

On the right part of the photo taken using a microcope under 40x magnification and using dark field illumination, we can see a curved vertical line on the right side of the photo, on the top. It is the area where the fissure reaches the surface of the ruby. Note that this line is continuous. It means that the fissure is not healed. Close to the surface, the fissure is filled and it is possible to see inside the fissure some strait lines that are in fact devitrification features and small round features (in fact gas bubbles). Deeper inside the fissure (on the left side of the photo) we can see some fingerprint like designs first something like honey combs, then something more like a fingerprint design. It is the area deep inside the fissure where some healing was taking place.

Photo: V. Pardieu / GIA Laboratory Bangkok, 2010

To illustrate the fact that we are not really facing a new treatment, it is interesting and useful to remind and study carefully the excellent diagram published in 1998 by Prof. H.A.Hänni (reproduced with permission). Prof. H.A.Hänni was trying to explained what was going on inside these fissures during the flux-assisted heat treatment process:

"Flux assisted healing process by H.A.Hänni (Reproduced with permission)"

It is interesting to see that Prof. Hänny already saw devitrification features in surface reaching lass filled fissures during the 1990's in the case of rubies heated with flux (nothing really new in this treatment then...):

- In "D. after possible devitrification" we can see that the surface reaching area is filled with glass, with gas bubbles and devitrification features (it is exactly what you see on the inclusion photo in this blog) but we can see also that after D, there is E (logic...):

- "E. after cleaning by surface-etching": Flux healed rubies were usually cleaned and the glass was removed before the stones to be released in the market.

This last step in the process was obviously not performed in the case of the stones which were recently submitted at the GIA labs as we saw commonly that glass was still present in some surface reaching fissures. This is the new thing and the issue here:

- If the fissure is healed, then it is closed by recrystalization of ruby (synthetic ruby) and thus the final product is stable.

- Now if it is just filled, the durability of the final product will depend on the durability of the filler...

As such stones with healed and also glass filled fissures were becoming more commonly submitted at the GIA labs, at the end of March 2010, the GIA gemological laboratories in Carlsbad, New York, and Bangkok started to issue reports disclosing clearly the presence of these filled fissures in addition to the healed fissures. The reason is that glass (with lead or without lead) is much less durable than ruby and glass as a filler is likely to get damaged by chemicals, heat or abbrasion dparticularly during the stting or jewelry repairing process.

Thus it is important that the presence of such filler is disclosed to the consumer.

To get more details about this issue and the research we dit at GIA, please read the following report:

Here is a link to the Mozambique special issue where you can find this study: "FAPFH/GFF Treated Ruby from Mozambique, a preliminary report" by V. Pardieu, N. Sturman, S. Saesaew, G. Du Toit and K. Thirangoon released May 11, 2010.

Hoping that you will find all that interesting and useful!

All the best,