The timeless appeal of emerald can be summed up in three words written in the year 50 AD: "Nothing greens greener." Roman historian Pliny the Elder was explaining the desire for the supreme green gem not only in Rome but throughout the ancient world.

Cleopatra, Egypt's tempestuous female monarch, was as famous for wearing emeralds in her time as Liz Taylor, the actress who played her in a 1969 movie, is for wearing diamonds in ours. Mummies in ancient Egypt were often buried with an emerald on their necks carved with the symbol for verdure, flourishing greenness, to symbolize eternal youth.

Islamic texts describe the Garden of Paradise as carpeted with emerald. The Moguls of India, including Shah Jahan, the builder of the Taj Mahal, loved emeralds so much they inscribed them with sacred text and wore them as talismans. Some of these sacred stones, called Mogul emeralds, can still be seen in museums and collections today.

The emeralds the ancients adored, from mines in Egypt and perhaps what is now Afghanistan, were nowhere near as beautiful as those mined today. The modern emerald bounty began almost five centuries ago when Spanish explorers arrived in the new world. Montezuma presented Cortes with a staggering emerald crystal much larger and finer than any ever seen before.

Emerald is most often cut in a rectangular step-cut, which is now popularly known as the emerald cut. Smaller sizes are also found in rounds, ovals, pear shapes and marquise cuts. You may have to look a while for an unusual shape in a larger size. Due to their rich color, emeralds are also spectacular when cut in a smooth-domed cabochon cut.

Emeralds, among the rarest of gems, are almost always found with birthmarks, known as inclusions. S ome inclusions are expected and do not detract from the value of the stone as much as with other gemstones. However, you should look to make sure that fissures do not go too deep into the stone so that it might be weakened enough to break if it were hit accidentally. The fissures that are characteristic of emerald are traditionally filled with oil or resin to make them less visible to the eye. You should assume that your emerald has been improved in this way unless it has a laboratory certificate indicating otherwise: such rare stones command a considerable premium.