Sterling Silver and 24K Gold Overlay, Opal and Amethyst Ring (Size 7)

Opals form when silica gel hardens in the cracks of other rocks. Most of the world's precious opal comes from Australia, where opal is the national gem. A boulder opal is an opal that has been sliced together with its surrounding ironstone for a varied look. Fire opal from Mexico comes in shades of orange and Peruvian opal is an opaque blue-green stone. An opal doublet has polished precious opal on the top with an ironstone backing added for strength, making the slice of opal less prone to chipping.