Marine oysters from the genus Pinctada are the principal source of saltwater pearls, whether formed naturally or cultured. These mollusks are found in the Pacific, Indian, and Atlantic Oceans. Gathering natural pearls is referred to as fishing, hunting, or pearling. Usually, people dive to gather these creatures and remove the organic gems inside. Unfortunately, few Pinctada oysters yield pearls. (This is especially unfortunate for the oyster, which dies when taken from its home and opened in this fashion, pearl or no pearl). Natural undersea beds of pearl-producing oysters are now very rare. For thousands of years, pearls have been highly prized for jewelry. The demand for the saltwater version of the June birthstone remains strong, though now it's met mainly through cultivation.
Saltwater Pearls Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Saltwater Pearls Information
|Is a Variety of||Pearl|
|Colors||See "Identifying Characteristics" below.|
|Specific Gravity||See "Identifying Characteristics" below.|
Freshwater and saltwater pearls form in the same manner. An irritant trapped in an oyster or other mollusk stimulates the production of nacre and the formation of the pearl. Although both varieties share most of their chemical and physical properties, the marine specimens have historically set the standard of beauty for the appearance of all pearls. Natural freshwater pearls have more irregular shapes and poorer luster. With improved cultivation techniques, farmed freshwater pearls can now match their saltwater brethren in appearance.
Identifying Characteristics of Saltwater Pearls
- Persian Gulf Pearls: Typically, creamy white or rose colors. Specific gravity (SG) is 2.68-2.74.
- Gulf of Manaar Pearls: Typically, a pale, creamy white color, sometimes with fancy overtones of blue, green, and violet. SG 2.68-2.74.
- Australian Pearls: Silvery white to yellow. SG 2.67-2.78.
- South Sea Pearls: Usually, white color with little orient but also yellow, gray, and black, with a characteristic metallic, grayish cast.
- Japanese Pearls: White, often with a greenish tinge. SG 2.66-2.76.
- Venezuelan Pearls: Colors may vary from white to bronze, also black. White pearls may be very iridescent and almost glassy. SG 2.65-2.75.
- California: Abalone, a group of shelled marine snails, may produce pearls of green, yellow, blue, and other tones. SG 2.61-2.69.
Cultured Saltwater Pearls
For more information on pearl cultivation techniques, see the main entry for pearl gemstones.
Grown in Pinctada fucata or Akoya oysters, Akoya pearls are the traditional cultured saltwater pearls. Raised primarily in Japan and China, their sizes range from 2 mm to 10 mm, though most are 5 mm to 7 mm in length. Usually, they have a white to cream body color but can occur in several other colors as well. If that weren’t enough, dyeing can turn Akoya pearls into any imaginable color. Unfortunately, pollution and illness have greatly impacted Japanese saltwater farms.
South Sea cultured pearls are grown in silver-lipped and gold-lipped Pinctada maxima oysters. Farms are found throughout the Indian and Pacific oceans, around Australia, Indonesia, Myanmar, and the Philippines. Larger than Akoyas, these pearls are usually 8 mm to 14 mm in diameter with white to gold body colors and low luster.
The famous Tahitian black cultured pearls are grown in black-lipped oysters, Pinctada margaritifera. Raised primarily in the waters of French Polynesia, they tend to be large like their South Sea cousins, ranging from 8 mm to 14 mm. These organic gems have black or very dark body colors with prominent overtones of green and purplish pink.
Abalones produces both whole and blister pearls, usually green, yellow, or blue. Both the shell and the pearls are highly distinctive, with dark coloring and bright iridescence. A popular food item, natural abalones are becoming rare, especially on the California coast. Farms now raise them to meet culinary demands. In nature, the creatures grow to a foot or more in length. However, the farmed variety isn’t allowed to grow over 4”. If you have a shell over that length, you have a natural specimen for sure.
- Persian Gulf: The world’s major pearl producing area, especially the coasts of Iran, Oman, and Saudi Arabia. For over 2,000 years, these waters have produced pearls. Persian Gulf pearls are usually small (less than 12 grains). During the diving season (May-September), hundreds of small boats work these waters. The diving depth is about 30′-90′ but usually less than 60′. Pearls are recovered from oysters, washed, and then sold to merchants in Bombay, India. Then, bleaching (using hydrogen peroxide and sun-light), sorting, grading, and drilling operations follow. In general, poor-quality pearls go to the Far East. Better pearls go mostly to Paris. From there, many reach the United States. Bombay is chiefly a brokerage center. Historically, Persian Gulf pearls have been called “oriental pearls,” a term then used for all natural saltwater pearls. Today, the term “oriental pearls” refers only to natural Persian Gulf specimens.
- Gulf of Manaar: An arm of the Indian Ocean, between Sri Lanka and India. An important source for more than 2,500 years, this area offers only sporadic fishing today. The Sri Lankan government controls the fishing and auctions the oyster haul. The oysters are opened by leaving them on the ground to rot. Then, people search the decomposed matter for pearls. Typically, the pearls go to Bombay.
- Australia: Divers in armored suits fish for pearl oysters off the west, northwest, and north coasts. Shell recovery is a major industry, as important as pearl recovery.
- South Seas: Native fisheries operate around Micronesia and Polynesia. These pearls may grow large and generally round. Tahiti is the major pearl center.
- Japan: Japanese waters are rapidly becoming too polluted for the natural existence of Pinctada. Today, cultured pearls constitute a much bigger industry.
- Venezuela: Usually, Venezuelan oysters produce small pearls.
Sometimes, jewelers measure individual pearls in grains. One grain equals 0.25 carats. (Please Note: a grain as a unit of measurement has other values when used for other materials, such as gold).
The following are some of the most celebrated saltwater pearls.
- “The Hope Pearl,” British Museum of Natural History (London). 2” long, 4.5” in circumference at the broad end, 1,800 grains. A saltwater pearl, possibly from Myanmar.
- “La Pelegrina,” found near the Isle of Margarita, West Indies, 133.16 grains. Survived both the French and Russian Revolutions.
- “La Peregrina,” found near Panama in 1560, 203 grains. Among its owners: Queen Mary I of England (“Bloody Mary”) and Elizabeth Taylor.
- “The Gogibus,” found in the West Indies, 504 grains. Once the largest pearl known in Europe. Lost for over 300 years until it resurfaced in 2009.
- “La Regente,” 337 grains. Purchased by Napoleon for Empress Marie-Louise.
- “The Pearl of Asia,” found in the Persian Gulf in the 17th century, 2,420 grains. The largest known saltwater pearl in the world, excluding the “Pearl of Lao Tzu,” which is a tridacna pearl, a kind of calcareous concretion.