Doublets generally consist of two individual layers. The first is that of a black backing. This is typically made out of black industrial glass but can also be made of black potch (opal with no ‘play of colour’ and therefore valueless), hard plastic, or brown ironstone. The second layer consists of a thin slice of precious opal. In most cases, these slices will be of white opal or crystal opal. The thickness of this layer will vary from stone to stone but it is generally found to be thicker than in triplets. The edges of the opal slice are generally shaped to give the stone a cabochon look (domed top).
It is easy to identify a doublet by searching for the place in which the opal slice and the black backing have been glued together. The finest doublets will have a lining that is perfectly straight indicating precision in the attachment process.
A triplet is similar to a doublet, but consists of three individual layers that are glued together. Like a doublet, a triplet also adopts a black backing, along with a thin slice of opal. The third layer is usually clear glass, plastic capping or quartz cut in the shape of a dome. The clear capping of the third layer may magnify the vibrancy of the opal, but it is meant to protect it from the environment.
The clear non-opal capping makes it extremely easy for professionals to identify whether a stone is a triplet or not. The way in which the light reflects off these stones is very different from that of other kinds of opals. The value of a triplet will be heavily dependent on the amount of opal used in making the stone, and is usually less than that of a doublet. That being said, such stones are generally found to be more resistant to damage and impact as a result of the extra third layer.
Caring for Doublets and Triplets
Since these two kinds of stones use adhesive in their makeup, it is possible that prolonged exposure to water may affect the way in which the stones are held together. When water is infused in between the layers, the stone will take up a ‘foggy’ appearance. It is always recommended to use a damp soft cloth and mild detergent when cleaning these stones, as opposed to more powerful chemicals bleaches and cleaners.