A black opal makes a gift that feels personal, and a loose stone lets you choose how it is worn. Many gift buyers start by searching for Ethiopian black opal earrings, and then find it is easier to buy the stone first and ask a local jeweler to make the piece.
Opal also weighs less than most other gems of the same size. In earrings, that means the stone feels light on the ear, even when it is large. If you are not sure about the ring size or the metal the person likes, a pendant or earrings are the safer gift, because they do not need a size.