Moonstone is a type of feldspar, the most abundant mineral group in the crust of the Earth. Feldspar is primarily composed of silicates of aluminum with traces of other minerals such as sodium and calcium. When feldspar forms with potassium and attains a translucent, pearly appearance, it is known as a moonstone. The name comes from the resemblance it has to the moon, and these stones have been used in jewelry, especially for women, for centuries.
Several parts of the world, including Sri Lanka, have deposits of moonstone. It is classified as an orthoclase, meaning that it forms around volcanic and hydrothermal deposits, and has a translucent appearance, along with a shimmering luster. Moonstone is a type known as adularia, after the Adula Mountains of Switzerland, where the stone is abundantly distributed. Adularia crystallizes at a low temperature, and when it takes the form of an opalescent stone, it is classified as a moonstone.
When found in the rough, moonstones are not an impressive sight. A skilled stone cutter must bring out the luminous appearance of the stones, which must be cut with care. Typically, they are cut in the form of a cabochon, a rounded and polished cut that lacks facets. The cabochon can take any form, although teardrop, round, and oval shapes are all common. If cut properly, the stone will shimmer and flow, exhibiting a property called adularescence, after the family of rock that these stones come from.
All moonstones possess a bluish to white hue, although the base color of the stone can be clear, white, yellow, orange, or gray. They must be handled with care, because moonstones are soft and brittle. If mishandled, they can scratch or break easily, although small scratches can be repaired with refinishing, which will reduce the overall size of the stone. Most moonstone jewelry is designed to protect the stone while showcasing its adularescent quality, and wearers should make sure that they are well seated in their mountings.
Although appropriate in men's jewelry, moonstone appears more often in pieces designed for women. Large cabochons can be used in necklaces and bracelets, while smaller stones are used in earrings and rings. Moonstone can be gently wiped with a soft cloth, and oiled if it loses luster, but wearers should avoid exposing it to excessive light and harsh chemicals, and remove the jewelry to prevent it from being submerged in water.