Richard Walter, age 9, of Peoria, I11., for his question:

WHERE DO YOU FIND THE BEST OPALS?

Opals from New South Wales in Australia are considered to be the most prized in the world. The gems are deep¬glowing blac k and are lighted by rich flashes of reds and yellows as well as greens and blues.

The opal is unique in the world of gem stones because it is not found in nature in the form of crystals. Instead it is found in irregular patches, often filling cavities in rocks. It is called a hydrated silica gel by gemologists because it contains water along with silica. The gem’s color flashes are caused by the water in the stone.

Opals are never cut with facets, like diamonds, since their beauty lies in internal color flashes. Instead, the stones are cut with gently rounded convex surfaces.