Pearl, one of the birthstones for June, is a hard object composed of calcium carbonate and produced within the soft tissue of a living shelled mollusk.
Rare natural pearls have been highly valued as objects of beauty for centuries, to the point where the word pearl has become a metaphor for something rare, admirable and valuable.
Pearls are known for being perfectly round, but contrary to popular belief naturally round pearls are very uncommon and expensive. Pearls come in a large variety of shapes and sizes, but most are off-round or oval shaped. They come in a variety of colors, ranging from light pink, to brown, green, blue and even black. Natural colours are mainly down to the breed of mollusc, but other influencing factors include diet, water temperature and pollutants.
The shine of a pearl is determined by the way light is reflected and refracted in its translucent layers. The overlapping of successive layers affects the stone's iridescence, so the thinner and more numerous the layers in the pearl, the finer its luster.
Pearl measures between 2.5 and 4.5 on the Mohs scale, so pearl jewelry suffers from the wear and tear of everyday use and should be treated with extra care.
Most natural oyster beds which produce pearls have vanished due to over-fishing, oil drilling and pollution, meaning all of today's pearls are created by pearl farmers under controlled conditions in China and Japan. These cultured pearls are the response to a tissue implant in either seawater oysters or freshwater mussels.
Pearl is mentioned in nearly every religion's ancient scriptures, and for thousands of years seawater pearls have been hunted by divers in the Indian Ocean, in areas including the Persian Gulf, the Red Sea, and the Gulf of Mannar. The Chinese also hunted for pearls in the South China Sea during the Han Dynasty, starting around 200BC.
Pearls were considered the ultimate symbol of wealth and social standing in Ancient Rome, and The Greeks held it in high esteem for both its beauty and association with love and marriage. At the height of the Roman Empire, it's believed Roman general Vitellius funded an entire military campaign by selling just one of his mother's pearl earrings.
Up until the beginning of the 20th century, pearl hunting by diving was the most common way of harvesting pearls, hence why they were considered so valuable. Spanish conquistadors discovered pearls around Central and South America, and were able to sell them in Europe and India, but a combination of overfishing and the industrialization of the United States had caused a depletion in the number of pearls found by the 1800s.
The process of culturing pearls was patented in 1916, and in 1928 the first small commercial crop of pearls was successfully produced. Pearl farming is now the most common means of producing pearl.
The value of pearls in jewelry is determined by a combination of color, size, lack of surface flaw, symmetry, and most importantly luster.
Ideally, the perfect pearl would be silvery white, very reflective and contain no surface blemishes. Larger pearls are also more valuable, all other factors being equal. Large, perfectly round pearls are the rarest and highest valued.
Pearls are routinely bleached with hydrogen peroxide to lighten them and make their color more consistent. Dye is often used to improve the appearance of lower–quality pearls by enhancing their color.
Some pearls are irradiated to give dark gray colors, and some are also reportedly treated with a colorless hard coating in an attempt to make them more durable.
Pearls have been associated with beauty for thousands of years, and pearl earrings and necklaces are still popular today. Over time it has become the symbol of purity and innocence. It is often sewn into bridal gowns, or worn as jewelry by the bride.
Although pearl is seen as a versatile option in jewelry which looks good with anything, it is also a relatively weak gem which is exposed to damage and requires extra care.