genuine opal doublet is set in handmade sterling silver ring. The opal is mostly greens and blues with some flash of red at certain angles. The ring size is 6 1/2 An opal doublet is a slice of precious opal glued to a black backing. This technique is used frequently with rare opal to produce larger and stronger pieces at a lower cost. The black backing, usually made of vitriolite or common opal, also causes the color of the opal to become darker and more vibrant.