Opal Treatments and Synethetics

Doublets and Triplets

When a peice of precious opal is too thin to be cut into the usual cabochon (dome shape with a flat back), it is layered with another material to increase its size. A “doublet” is a thin layer of precious opal with a backing or “base” of another, darker material. A dark material is chosen to bring out the play of color in the opal. The best material is dark “common opal” (less valuable opal without play of color).

To make the opal look even larger and more like an actual cabochon, a dome of clear crystaline material is placed on top. This creates an illusion of a solid opal stone. The finished product is called a “triplet.” Only by looking at a certain angle from the side can you tell that it is a doublet and not a natural opal cabochon.


Common treatments of precious opal are resins or waxes to seal the cut stone. This improves the shine and protects it from dehydration.

Opal is sometimes “smoked” to make crystal opal or white opal look more like black opal. This treatment is difficult to detect, so when shopping you will most likely have to rely on the reputation of the seller and his disclosure. An opal that has been treated to become dark is more valuable than a white opal, but less valuable than a naturally dark opal.


Immitations of opals are not very common. There is a plastic immitation that looks very much like opal but. It’s hardeness and low melting point distinguish it from natural opal. There is also a realtively recent “lab created” opal which is distinguishable by its “too perfect” harlequin pattern.

An honest seller will always disclose these things. However, it is important for you to understand you they affect the value of the opal. And it’s always a good idea to ask to make sure.

Here is an Illustration of Treated Opal, Opal Doublet and Triplet and Created Opal:

Treated Opal:This opal has been treated with a coating of resin to smoothen the tiny pits, improve shine and seal moisture. This treatment is very standard and difficult to detect with the eye. Opal Doublet: From the side, we can see the dark backing behind the natural slice of opal. Opal Triplet: We can see the dark backing material and the quartz cabochon “cap.” The thin layer of opal in between is hard to see but from the top, this would look like a normal opal cabochon. Synthetic Opal: The very defined color patches and full spectrum color range of this opal make it seem to good to be true. It is. It was made by Gilson labs. All other factors being equal, a synthetic opal will always be cheaper than a natural one.


How the TYPE affects the value of an Opal
How COLOR affects the value of an Opal
How PATTERN affects the value of an Opal
How CUT affects the value of an Opal
Opal treatments and synthetics
Opal meaning and symbology
Opal myths and misconceptions