It was a guided, historical tour complete with excellent photos to support his talk.
Chris shared that very few stones are completely untreated, that many are oiled! A stone may be untreated with heat but still may have oiling so it is important to examine for fissures reaching the surface. One particular photo series showed a wonderful-looking stone with the oil present and a dramatically different-looking stone after the oil had been leached.
Most are familiar with the more common treatments of heat which include flux healing and beryllium and chromium diffusion. He also cautioned against assuming that the presence of needles is proof of “no heat” Not true! The needles melt at 1300C. The stone may still have had low heat treatment. Heating of stones began in the 1970’s and continues to day in various forms and is done to improve colour. The 1980’s brought flux-assisted heating and this was to improve clarity and stability.
2003 began the latest gemological and ethical challenges with the advent of the glass filled and “composite” stones. Some stones are simply glass-filled while others are composed of ruby gravel and fused together with glass and then fashioned into stones. These particular stones have inherent durability problems and require very special care when setting, cleaning and with daily use.
Chris believes that all of this notwithstanding, these stones do have a place in the market as long as FULL disclosure takes place. For more information on these stones, visit http://www.aglgemlab.com/
Meeting Summary by Sherlene Y. Bradbury, G.G. Senior Member NAJA
Pictures by Bobby Mann, G.G.