A Pearl is a smooth, round growth formed naturally within the shell of a mollusk due to an irritant and used as a gem. A Pearl is a hard, roundish object produced within the soft tissue (specifically the mantle) of a living shelled mollusk. Just like the shell of mollusks, a Pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal Pearl is perfectly round and smooth, but many other shapes of Pearls (baroque Pearls) occur. Long known as the "Queen of Gems," Pearls possess a history and allure far beyond what today's wearer may recognize. Throughout much of recorded history, a natural Pearl necklace comprised of matched spheres was a treasure of almost incomparable value, in fact the most expensive jewelry in the world. Now we see Pearls almost as accessories, relatively inexpensive decorations to accompany more costly gemstones.
Ever since the ancient Egyptians first started creating jewelry, Pearls have become one of the highest regarded gemstones. Even today Pearls still hold their value due to the rarity of "mother nature" creating this form of jewelry. The Arabs have shown the greatest love for Pearls. The depth of their affection for Pearls is enshrined in the Koran, especially within its description of Paradise, which says: "The stones are Pearls and jacinths; the fruits of the trees are Pearls and emeralds; and each person admitted to the delights of the celestial kingdom is provided with a tent of Pearls, jacinths, and emeralds; is crowned with Pearls of incomparable lustre, and is attended by beautiful maidens resembling hidden Pearls."
Prior to the 19th century, when they were superseded in price by diamonds, natural Pearls had, throughout history, been valued above all other gems. Although their beauty, and the fact that they come out of the mollusk ready to use, were important factors, it was sheer rarity that drove their value to the highest levels. The formation of a large, beautiful and perfect natural Pearl is an event so unlikely in Nature that only those at the pinnacle of wealth and power in a society were able to own them. Depending on the species between 1/1000 to 1/500,000 mollusks will form Pearls during their lifespan, and the vast majority of those formed will be small, off-color or flawed.
Pearls, in fact, played the pivotal role at the most celebrated banquet in literature. To convince Rome that Egypt possessed a heritage and wealth that put it above conquest, Cleopatra wagered Marc Antony she could give the most expensive dinner in history. The Roman reclined as the queen sat with an empty plate and a goblet of wine (or vinegar). She crushed one large Pearl of a pair of earrings, dissolved it in the liquid, then drank it down. Astonished, Antony declined his dinner -- the matching Pearl -- and admitted she had won. Pliny, the world's first gemologist, writes in his famous Natural History that the two Pearls were worth an estimated 60 million sesterces, or 1,875,000 ounces of fine silver ($9,375,000 with silver at $5/ounce).