Opal doublets and triplets are a montage, a thin genuine opal is joined together with another material. Triplets and doublets are in most cases cheaper then solid opal stones due to the thin slice of opal and it can be manufactured many from one rough opal. A doublet or triplet has generally the same lustre as similar solid opal.
A Doublet is built with two layers joined together with glue.
A thin slice of opal is glued one a backing of glass, plastic or opal material.
The thickness of the opal can vary but is in most cases thicker then in a triplet.
A Triplet is built in three layers. Built as a doublet, but with a third layer of quartz or glass over the opal.