Unlike most gemstones that are found within the Earth, pearls have an organic origin. They are created inside the shells of certain species of oysters and clams. Some pearls are found naturally in mollusks that inhabit the sea or freshwater settings such as rivers. However, many pearls today are cultured-raised in oyster farms that sustain a thriving pearl industry. Pearls are made mostly of aragonite, a relatively soft carbonate mineral (CaCO3) that also makes up the shells of mollusks.
A pearl is created when a very small fragment of rock, a sand grain, or a parasite enters the mollusk’s shell. It irritates the oyster or clam, who responds by coating the foreign material with layer upon layer of shell material. Pearls formed on the inside of the shell are usually irregular in shape and have little commercial value. However, those formed within the tissue of the mollusk are either spherical or pear-shaped, and are highly sought out for jewelry.
Pearls possess a uniquely delicate translucence and luster that place them among the most highly valued of gemstones. The color of the pearl depends very much on the species of mollusk that produced it, and its environment. White is perhaps the best-known and most common color. However, pearls also come in delicate shades of black, cream, gray, blue, yellow, lavender, green, and mauve. Black pearls can be found in the Gulf of Mexico and waters off some islands in the Pacific Ocean. The Persian Gulf and Sri Lanka are well-known for exquisite cream-colored pearls called Orientals. Other localities for natural seawater pearls include the waters off the Celebes in Indonesia, the Gulf of California, and the Pacific coast of Mexico. The Mississippi River and forest streams of Bavaria, Germany, contain pearl-producing freshwater mussels.
Japan is famous for its cultured pearls. Everyone familiar with jewelry has heard of Mikimoto pearls, named after the creator of the industry, Kokichi Mikimoto. Cultured pearls are bred in large oyster beds in Japanese waters. An “irritant,” such as a tiny fragment of mother-of-pearl, is introduced into the fleshy part of two- to three-year-old oysters. The oysters are then grown in mesh bags submerged beneath the water and regularly fed for as long as seven to nine years before being harvested to remove their pearls. Cultured pearl industries are also carried out in Australia and equatorial islands of the Pacific.
The largest pearl in the world is believed to be about three inches long and two inches across, weighing one-third of a pound. Called the Pearl of Asia, it was a gift from Shah Jahan of India to his favorite wife, Mumtaz, for whom he also built the Taj Mahal.
La Peregrina (the Wanderer) is considered by many experts to be the most beautiful pearl. It was said to be originally found by a slave in Panama in the 1500s, who gave it up in return for his freedom. In 1570, the conquistador ruler of the area sent the pearl to King Philip II of Spain. This pear-shaped white pearl, one and a half inches in length, hangs from a platinum mount studded with diamonds. The pearl was passed to Mary I of England, then to Prince Louis Napoleon of France. He sold it to the British Marquis of Abercorn, whose family kept the pearl until 1969, when they offered it for sale at Sotheby’s. Actor Richard Burton bought it for his wife, Elizabeth Taylor.
Pearls, according to South Asian mythology, were dewdrops from heaven that fell into the sea. They were caught by shellfish under the first rays of the rising sun, during a period of full moon. In India, warriors encrusted their swords with pearls to symbolize the tears and sorrow that a sword brings.
Pearls were also widely used as medicine in Europe until the 17th century. Arabs and Persians believed it was a cure for various kinds of diseases, including insanity. Pearls have also been used as medicine as early as 2000 BC in China, where they were believed to represent wealth, power and longevity. Even to this day, lowest-grade pearls are ground for use as medicine in Asia.
June’s second birthstone is the moonstone. Moonstones are believed to be named for the bluish white spots within them, that when held up to light project a silvery play of color very much like moonlight. When the stone is moved back and forth, the brilliant silvery rays appear to move about, like moonbeams playing over water.
This gemstone belongs to the family of minerals called feldspars, an important group of silicate minerals commonly formed in rocks. About half the Earth’s crust is composed of feldspar. This mineral occurs in many igneous and metamorphic rocks, and also constitutes a large percentage of soils and marine clays.
Rare geologic conditions produce gem varieties of feldspar such as moonstone, labradorite, amazonite, and sunstone. They appear as large clean mineral grains, found in pegmatites (coarse-grained igneous rock) and ancient deep crustal rocks. Feldspars of gem quality are aluminosilicates (minerals containing aluminum, silicon and oxygen), that are mixed with sodium and potassium. The best moonstones are from Sri Lanka. They are also found in the Alps, Madagascar, Myanmar (Burma), and India.
The ancient Roman natural historian, Pliny, said that the moonstone changed in appearance with the phases of the moon, a belief that persisted until the sixteenth century. The ancient Romans also believed that the image of Diana, goddess of the moon, was enclosed within the stone. Moonstones were believed to have the power to bring victory, health, and wisdom to those who wore it.
In India, the moonstone is considered a sacred stone and often displayed on a yellow cloth – yellow being considered a sacred color. The stone is believed to bring good fortune, brought on by a spirit that lives within the stone.
June’s third birthstone is the alexandrite. Alexandrite possesses an enchanting chameleon-like personality. In daylight, it appears as a beautiful green, sometimes with a bluish cast or a brownish tint. However, under artificial lighting, the stone turns reddish-violet or violet.
Alexandrite belongs to the chrysoberyl family, a mineral called beryllium aluminum oxide in chemistry jargon, that contains the elements beryllium, aluminum and oxygen (BeAl2O4). It is a hard mineral, only surpassed in hardness by diamonds and corundum (sapphires and rubies). The unusual colors in alexandrite are attributed to the presence of chromium in the mineral. Chrysoberyl is found to crystallize in pegmatites (very coarse-grained igneous rock, crystallized from magma) rich in beryllium. They are also found in alluvial deposits – weathered pegmatites, containing the gemstones, that are carried by rivers and streams.
Alexandrite is an uncommon stone, and therefore very expensive. Sri Lanka is the main source of alexandrite today, and the stones have also been found in Brazil, Madagascar, Zimbabwe, Tanzania, and Myanmar (Burma). Synthetic alexandrite, resembling a reddish-hued amethyst with a tinge of green, has been manufactured but the color change seen from natural to artificial lighting cannot be reproduced. Such stones have met with only marginal market success in the United States.
The stone is named after Prince Alexander of Russia, who was to become Czar Alexander II in 1855. Discovered in 1839 on the prince’s birthday, alexandrite was found in an emerald mine in the Ural Mountains of Russia.
Because it is a relatively recent discovery, there has been little time for myth and superstition to build around this unusual stone. In Russia, the stone was also popular because it reflected the Russian national colors, green and red, and was believed to bring good luck.
Find out about the birthstones for the other months of the year.