A pearl is a hard, rounded secretion formed inside the shell of certain mollusks, used as a gem.
It is built up of layers of aragonite or calcite held together by conchiolin. Its composition is identical to that of the “mother-of-pearl,” or nacre, that forms the interior layer of the mollusk shell. Pearls may be round, pear-shaped, button-shaped, or irregular (baroque) and are valued in that order.
There are six criteria for evaluating pearls–size, shape, color, luster and orient, surface purity and nacre thickness.
Pearls are characterized by their translucence and lustre and by a delicate play of surface color called “orient.” The more perfect its shape (spherical or droplike) and the deeper its lustre, the greater its value. Only those pearls produced by mollusks whose shells are lined with mother-of-pearl (e.g., certain species of both saltwater oysters and freshwater clams) are really fine pearls; pearls from other mollusks are reddish or whitish, “porcellaneous,” or lacking in pearly lustre. Pearls are not faceted or polished like other gems.
Pearl Colors vary with the mollusk and its environment. They range from black to white, with a rose’ tint esteemed most desired. Other colors are cream, gray, blue, yellow, lavender, green, and mauve.
Pearls come in a wide range of sizes. Those weighing less than 1/4 grain (1 pearl grain = 50 milligrams = 1/4 carat) are called “seed pearls.” The largest naturally occurring pearls are the “Baroque” pearls.
“Baroque” pearls are irregularly shaped pearls that have grown in muscular tissue; pearls that grow adjacent to the shell are often flat on one side and are called “Mabe'” pearls.
Jewelers commonly refer to saltwater pearls as “Oriental” pearls and to those produced by freshwater mollusks as “Freshwater” pearls.
Natural freshwater pearls occur in mussels for the same reason that saltwater pearls occur in oysters.
Foreign material, usually a sharp object or parasite, enters a mussel and cannot be expelled. To reduce irritation, the mollusk coats the intruder with the same secretion it uses for shell-building, nacre. A great irony of pearl history is that the least expensive cultured pearl product in the market today rivals the quality of the most expensive natural pearls ever found. Pearls from freshwater mussels lie at the center of the liveliest activity in pearling today.
Cultured Freshwater Mussels
To culture freshwater mussels, workers slightly open their shells, cut small slits into the mantle tissue inside both shells, and insert small pieces of live mantle tissue from another mussel into those slits. In freshwater mussels that insertion alone is sufficient to start nacre production. Most cultured freshwater pearls are composed entirely of nacre, just like their natural freshwater and natural saltwater counterparts. The Chinese were the first to culture a product from freshwater mussels.
The first cultured freshwater pearls originated in Japan.
Pearl farmers experimented with freshwater mussels in Lake Biwa, Japan. Initial commercial freshwater pearl crops appeared in the 1930s. The all-nacre “Biwa” pearls formed in colors unseen in saltwater pearls. Almost instantly appealing, their lustre and luminescent depth rivaled naturals because they, too, were pearls throughout.
A cultured saltwater pearl that comes primarily from Japan and China. Size ranges from 2mm to 10mm, and is used in most of the necklaces found in retail stores. “Akoya” overtone colors are rose and green and combinations of overtone and body colors are white-rose.
The largest Natural pearl center is the Persian Gulf, which is said to produce the finest saltwater pearls. Other important sources are the coasts of India, China, Japan, Australia, the Sulu Archipelago, various Pacific islands, Venezuela, and Central America, and the rivers of Europe and North America.
Black Tahitian Pearls
Because of their rarity, are often highly valued. Everything that makes the Tahitian pearl unique among gems–the size of the pearls, the colors, the mirror-like shine, the rainbow play of light–is the product of a perfect and precise combination of factors that exist nowhere else in the world. In the pearl oyster, it is the substance that makes up the inner lining of the shell, or the “mother-of-pearl”, as well as the pearl itself. Black Pearls are sorted according to their size, shape, color, luster and purity:
- Size: pearl size generally ranges from 8mm to 14mm. Some pearls can measure 16 or 18mm in diameter.
- Shape: Round (spherical) is the rarest and most sought after shape. The other shape categories are: semi-round, semi-baroque, button, oval, circled (grooved), drop and pear shape.
- Color: Tahitian cultured pearls are naturally gray and black, “peacock green,” “aubergine purple,” “marine blue,” and all shades of gray.
- Luster: The pearl’s luster is directly affected by its surface purity and the ability to reflect light. The fewer surface characteristics, the more “mirror-like” the luster.
- Purity: The surface of a pearl is judged by the fewest amount of blemishes, dents, scratches and stains. The fewer of these characteristics, the “purer” the pearl.
Black Tahitian pearl strands range in price from $2,500 to $25,000 per strand AA to AAA quality strands:
5-5.5mm = $275 – $600
6.5-7mm = $650 – $1,400
7.5 – 8mm = $850 – $2,000
8-8.5mm = $1,200 – $3,800
9-9.5mm = $2,700 – $6,000
9.5-10mm = $5,000 – $8,500
South Sea Pearls
Almost all South Sea Pearls are cultivated. As in the past, the pearl divers still exist, but today their role is to collect Mother of Pearl shells and deliver them to the pearl farms for the cultivation of South Sea Pearls. Unlike other cultured pearls, The South Sea cultivated Pearl consists predominantly of pearl material known as nacre. The quality and thickness of the nacre is the most important factor in determining a pearl’s beauty and value.
In the past, Burma (now Myanmar) was the leader in production of these beauties. It is now Australia that is the source of the majority of the world’s finest South Sea pearls. Nacre growth is much faster in the warmer South Sea waters, making these pearls rarely less than 10mm. Australian South Sea pearls are known for their fine luster and desirable pink-on-white colors. The Philippines are known for their light cream colors. Malaysia are known for their faint gray and faint blue colors. Indonesia is known for their bright, lustrous pink colors.
12mm to 14mm = $1,200 to $5,000
(Graduated Strands for necklaces)
12mm to 16mm = $25,000 to $75,000
DID YOU KNOW!