An opal doublet stone is a thin layer of light precious and natural Australian opal stone attached to a background made of black potch ( black opal stone without fire) or nowadays boulder stone from Queensland.
The opal used is an opal from Coober Pedy, in the State of South Australia.
It is an opal composite.
It costs a lot less than a solid opal stone and can last many years without deteriorating.
It is sensitive to water. Do not get it wet or immerse in water.