Are Pearls in Clams and Oysters?
While all mollusks, including oysters, mussels, and clams can technically make pearls, only some saltwater clams and freshwater mussels are used to commercially grow cultured gem-grade pearls.
Although technically any mollusc, such as an oyster, mussel, or clam, can produce pearls, only a few freshwater mussels and saltwater clams are employed to commercially create cultured gem-grade pearls.
Depending on a number of variables, the typical price range for oyster pearls can range from $20 to $5,000 or more per pearl. Natural pearls and those with excellent quality or deeper significance will command greater prices.
Pearls are hard, circular objects formed within the soft tissue of a living mollusk. They consist of calcium carbonate crystals deposited in concentric layers. The ideal pearl is round, smooth, and perfectly round. For centuries, natural pearls of high quality have been prized as gemstones. Clams and oysters are both freshwater and saltwater creatures that produce pearls. Pearls are formed within the oyster’s mantle, which is a layer of tissue surrounding the oyster’s body.
Oyster pearls are formed when the oyster is injured or exposed to an irritant. The irritant causes the oyster to secrete nacre as a natural defense. This nacre builds up and results in a gorgeous pearl. In some cases, a string of pearls can take years to form.
Natural pearls in clams and oyster are produced by mollusks living in ocean waters. Pearls are formed in oysters and clams as a protective mechanism against irritants. Once the irritant is inserted, the oyster coats it with a layer of nacre, also known as mother-of-pearl.
Before the 20th century, the most common way to harvest pearls was by hunting. Divers would manually collect oysters from the bottoms of rivers and oceans, checking each oyster for pearls. However, not all natural oysters produce pearls, and a haul of three tons of oysters may contain only three or four pearls.
The Persian Gulf has historically been a major source of natural pearls. In the early twentieth century, pearl oysters in the Persian Gulf were found in abundance off the coast of Bahrain. The cream-white pearls produced from these oysters are among the world’s finest. Other important sources include the Gulf of Manaar in Sri Lanka and the Red Sea. Lesser production occurs in the Gulf of Thailand, Burma, Venezuela, Tahiti, and New Guinea.
Cultured pearls are formed within a living oyster. Pearl-producing mollusks produce these pearls after a farmer inserts a small piece of mother-of-pearl shell into their tissues. This induces nacre secretion, the substance that covers the pearl. The pearl is then harvested after an average of 18 months or three years. In contrast, natural pearls are extremely rare and it would take hundreds of oysters to find a single pearl.
To create a pearl, mussels must open their shells. Pearl farm workers will then implant soft tissue of another mollusk into the oyster. This process is known as “culturing,” and is faster and easier than the natural process of growing pearls. Once the oyster is ready, it will secrete many layers of nacre around the implant.
In addition to the Chinese, the Japanese have also become interested in the process. In the twelfth century, they began growing oysters and clams containing Buddhas. The Buddhas eventually became coated with nacre, and the method became a popular way to harvest pearls. This method is similar to Chinese pearl farming. Once the pearl has been coated with nacre, the half shape is molded and placed against the oyster shell. It is then mounted on a backing for jewelry.
Cultured pearls in clams and ovaries are created through the process of aquaculture. This method requires the right conditions to grow pearls. Generally, a pearl has at least one mm of nacre beneath the surface of the mollusk. During the process, workers tend the mollusk until the pearls are harvested.
The process of pearl making in oysters is not a fast one. Pearls are formed due to irritation of the oyster’s shell, and then a layer of nacre is secreted in its innermost shell. This layer protects the oyster’s interior from irritants while allowing growth and shell repair.
The secretion of nacre from mollusks is responsible for the creation of pearls. The nacre is made up of a combination of minerals and proteins. These compounds coat the pearl’s exterior and form a thin layer called the mantle. This mantle reflects light and produces different colors when the light hits it at different angles.
The secretion of nacre begins when a foreign substance slips into an oyster. The irritant causes the oyster to secrete nacre, which covers the irritant. Over time, the nacre layer builds up and becomes a pearl.
Pearls can be natural or cultivated. They are valued for their luster and shape, as well as their size. However, not all nacreous pearls are cultivated. Pearls are graded based on their size, shape, color, and complexion.
Oysters and clams can produce pearls. However, pearl farmers select specific species of oysters for cultivation. During the harvesting process, pearl farmers cut a slit in the mantle tissue, and the oyster secretes nacre. This secretion process takes two to three years.
Oysters can produce both beautiful and less attractive pearls. In some cases, oysters can produce an odd-looking pearl, whereas other oysters produce a funny-looking chalky-looking thing. The funky-looking pearl is a nacreous pearl.
The formation process of non-nacreous pearls is different from that of nacreous pearls. These pearls are not formed by a crystalline structure, and therefore lack the luster of natural pearls. Despite being found in clams and oysters, these pearls are not iridescent, and the Gemological Institute of America recommends that they are categorized as non-iridescent porcelain-like ones.
The iridescence in the pearls comes from interference and diffraction processes. These processes occur due to the interplay of white light with tiny overlapping platelets of calcium carbonate. The thickness and number of the platelets determine the iridescence of the pearl.
Species of Mollusks that Produce Pearls
Pearls are formed when irritants lodge within the mollusk and produce a layer of nacre, also known as mother-of-pearl. The nacre is a combination of protein and mineral, and it forms a protective layer around the irritant. This nacre is then secreted by the mollusk to cover the irritant.
Pearls are produced by several species of mollusks, including clams and oysters. Most pearl-producing mollusks are bivalve mollusks that have two halves connected by a hinge. They have a soft body, paired gills, and a byssal gland. Pearl formation is a passive process, and it takes anywhere from six months to seven years to form a single pearl.
Pearls are formed by mollusks living in ocean water. Some species of mollusks produce gem-quality pearls, but not all. The majority of pearls are formed by free-ranging “wild” oysters. The nacre layer gives gem-quality pearls an opalescent sheen.
The mollusk’s anatomy varies slightly from the oyster and clam’s anatomy. The shell is secreted from the mantle, and many species have a tongue called the radula. Most mollusks also have a respiratory and circulatory system. Seventy percent of mollusk species are edible. The exception is the thorny oyster Spondylus, but even this mollusk is edible.
Characteristics of Pearls
Pearls grow in a variety of shapes. Some are round, others are slightly asymmetrical, and still others are baroque. The shape of a pearl is a crucial factor in determining its value. A perfectly round pearl is rare and therefore valuable. Pearls with irregular shapes, like baroque ones, are less valuable.
The shape of a pearl depends on its positioning in the shell. If the pearl is flat against the shell, it will form a ring or groove. These are called ringed pearls or circled pearls. Ringed pearls may also have a circular or oval shape. They are less common than spherical pearls and are often the most valuable.
Natural pearls are almost entirely composed of calcium carbonate and conchiolin. These crystals are formed in the shell of a bivalve mollusk. Although technically they are calcareous, pearls are iridescent. A pearl is formed by the secretion of calcium carbonate around an irritant inside the mollusk. The mollusk secretes the calcium carbonate and conchiolin to cover the irritant. A pearl can be round, oval, or irregular, but it is very rare to find a perfectly round pearl.
Some clams and oysters contain pearls. A keshi pearl has a nacre coating and is irregular in shape. Cultured pearls are seeded by placing a piece of the oyster’s mantle muscle or a bead of mother of pearl inside the shell. The oyster will then produce a pearl surrounding the mantle piece.
Pearls are a result of a complex process. During the shell opening process, oysters may accidentally let something inside. This could be a parasite or irritant. In such cases, the oyster covers the foreign object with nacre, and the nacre forms layer upon layer until the oyster produces a pearl.