Doublet
Definition:
A doublet is a gemstone sandwich, a gem that's created from layers. The lower, larger portion of a doublet is made from glass or an inexpensive stone; the thinner, more desirable gem is adhered to the top of the inexpensive slice.
Opal doublets are common, and should always be disclosed. Buy gems from a retailer you trust, and ask questions before making a purchase.
Triplets are similar to doublets, but are made up of three layers.
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