Historically, opal has been one of the few gemstones rarely subjected to any treatments. Sugar & acid carbon deposition used to be the predominant treatment applied to only a very specific and scarce type which then resembled natural black opal. However, the discovery of several deposits of gem quality opal in Ethiopia has resulted in a dramatic revision of this rule of thumb.
The extraordinary hydrophane characteristic of the majority of the opals from Ethiopia has opened up the opportunity to introduce a wide range of new treatments including smoke, colored dyes and a variety of synthetic resins which are intended to stabilize the opals and prevent cracking.
The conclusion will be the presence of evidence for and/or against the rumor that almost all the Ethiopian opals currently available in the market are treated without proper disclosure from the gemstone seller.
