Pearls, June's Birthstone

June has three choices for birthstones: pearl, alexandrite and moonstone. Pearls have been used as adornment since the dawn of civilization. A Sumerian clay tablet mentions pearls as early as 2300BCE. Pearls, according to South Asian mythology, were dewdrops from heaven that fell into the sea. Dewdrops were caught by shellfish under the first rays of the rising sun, during a period of full moon. 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. Pearls are organic gems from different bi-valve 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, which responds by coating the foreign material with layer upon layer of shell, called nacre. The color depends on the type of creature and the environment where it is produced. Prior to the 20th century all pearls were natural and found in mollusks and oysters. In the early 20th century pearls began to be cultured, originally by Kokichi Mikimoto of Mikimoto Pearls. Since the 1920’s cultured pearls have almost completely replaced natural pearls in the market. 

There are four types of cultured pearls, Akoya, South Sea, Tahitian and Freshwater.   The Akoya, South Sea and Tahitian are all saltwater cultured pearls. Akoya pearls are cultured in Japan, China and Vietnam in the Pinctada fucata oyster. Akoya comes from the Japanese word for oyster. The size range for Akoyas are 2 – 10 mm, the average is 6 – 7mm.  The classic color is white with a slight pink overtone and high almost mirror like luster.

South Sea pearls are cultured in Australia, the Philippines and Indonesia in the Pinctada Maxima oyster. The colors are whites and golden and range in size for 7mm to 18mm the average falling between 10mm – 15mm.  The luster is a soft and satiny. Large, round South Sea pearls are often in sell matched strands. Large rounds are also used in as a single pearl in rings, drop pendants and earrings. Large rounds are more difficult to culture, and often become misshapen as they grow. These misshapen pearls when they are now longer round are called baroque pearls and are often used in strands or as separate pearls in earrings and necklaces.

Tahitian pearls are cultured in Polynesia in the Pinctada margaritifera oyster. These pearls are all in the black ranges, greens, blues and other unusual colors with high luster. Pistachio, aubergine and peacock are some of the names of the colors of these pearls. Well-matched strands of large, lustrous Tahitian pearls of unusual colors command high prices. As  a result many Tahitian pearls are sold as singles or pairs in rings, pendants and earrings.

Freshwater pearls are cultured in mussels, the most common is the Hyriopsis cimingi. Most of the freshwater pearls are cultured in China, with Japan and the United States producers as well. The size range on freshwater pearls are 2mm – 13mm, the average sizes 6mm – 10mm, most are not round and are many different shapes and colors. Production is high volume and most are reasonably priced. 

For more information on pearls see the Gemological Instute of America.