Doublet Opal Stone
The stone name opal comes from the Sanskrit word “Upala” for stone or precious stone.
Doublets consist of two layers adhered together with glue:
A black backing which is made of either black industrial glass, black patch (colourless opal), hard plastic, brown ironstone or sometimes vitrolite.
A thin slice of opal (normally crystal opal or white opal). The thickness of the opal in a doublet can vary, however, it is generally thicker than the opal found in a triplet. The edges of the slice of opal are generally rounded off (if there is enough opal) to give the stone a cabochon (domed top).
Doublets can usually be identified by looking at the side of the opal – if the stone has been adhered together you will notice that the line where the coloured opal and the black backing meet is perfectly straight. This is necessary for the two layers to be adhered together. If a doublet is set into jewellery with the sides covered, it is extremely difficult, even for an expert, to tell whether it is a doublet or a solid opal. Since the top of the stone consists of pure opal, it, therefore, appears exactly like a black opal, and doublets thus have a much more natural appearance than triplets.