Emerald is the green form of beryl, a group of gemstones that include aquamarine in the blue form, the lovely pink morganite, golden heliodore and goshenite, which is white. Beryls are considered precious gems, and emerald, with its brilliant green color, is one of the most prized of gems. Natural emerald is rare, and even the stones in fine jewelry in the stores are often simulated rather than genuine. Almost all genuine emerald is oiled for its own protection, as this fills any fissures in the stone. The finest emerald is clear, but the opaques, much less costly, and often color enhanced, can be lovely additions to jewelry!