Jean Forman, age 9, of Omaha, Neb., for her question:

HOW DOES A MOONSTONE CHANGE COLORS?

Moonstone is the birthstone for June. It can be cut and used as a gem. Light will shine through the stone, but not as clearly as it does through glass. The stone seems to change color because of some reflective material that is part of its composition. Light will be reflected in first 'a bluish and then a pearly colored sheen because of the stone's inside structure.

Many of the world's best moonstones come from Sri Lanka.  A moonstone is actually a milky, translucent alkali feldspar. And a feldspar is the most abundant mineral in the rocks at and near the earth's surface. All feldspars contain aluminum and silica but the varieties differ in the amounts and kinds of other elements that are present.