Pearls: Types, Qualities, Sources, Treatments and Jewelry Styles

Pearls: Types, Qualities, sources, Treatments, and Jewelry Styles   by Renée Newman

Thanks to new and better methods of cultivating freshwater pearls, their sizes have been increasing, their quality has improved and their shapes have become more varied. They now compete with Tahitian and Australian cultured South Sea pearls in terms of beauty and size. As a result, cultured freshwater pearls and South Sea pearls are being combined in high-end jewelry. Renée’s presentation showed exquisite examples of how designers are using the various types of pearls as well as colored gems to create unique pearl jewelry.

The beginning of her presentation compared traditional white bleached Akoya pearls to natural color unbleached Akoya pearls, which have recently entered the market. Akoya cultured pearls are saltwater pearls that are round and usually less than 10 mm in size. They were the first pearls cultured and sold by the Japanese. Today Akoya pearls are also cultivated in China, Vietnam, Sri Lanka and the UAE using the Pinctada fucata, Pinctada martensii, or Pinctada radiata oysters.

Top quality Akoya cultured pearls have a high luster, a nacre thickness of at least 4mm and a smooth surface. The fewer the blemishes and the more round the pearls are, the higher their price. Nevertheless, baroque shaped pearls with blemishes can be quite attractive and are more affordable. White to pink Akoya cultured pearls sell for more than those that are cream or yellowish colored. Even though well-matched strands generally cost the most, multicolored strands have become popular in recent years.

Freshwater pearls are “farmed” in lakes and ponds. The most amazing point that Renée told us was that freshwater mussels can produce up to 40-50 pearls at ONE time ~ whereas salt water pearls are grown one pearl at a time.  No wonder they are so much more expensive.  Renée showed a large mussel that contained a bunch of multi-colored, multi-sized pearls.  She was standing there when the shell was opened and took a picture of the resulting “haul” after they were simply rinsed off and dumped into a cup.  Freshwater pearl mussels can grow pearls 2 or 3 times over a period about 7–10 years. Some wild mussels have lived as long as 130 years.

If a pearl grows attached to the shell, it is called a blister pearl, and if it is formed in the interior of a mollusk, it is called a whole pearl, free pearl or cyst pearl. The Chinese cultivated blister pearls in the shape of Buddha as long ago as the 13th century, but it took the Japanese to devise a way to culture freshwater whole pearls in Lake Biwa in 1925.  By 1930, they were selling them commercially overseas.

The first Chinese freshwater pearls were produced in the late 1960s and were grown by inserting a tiny piece of donor mantle tissue into the mantle of a live mussel. These pearls were solid nacre and had no shell bead nucleus so are called “beadless pearls.”  Chinese beadless cultured freshwater pearls didn’t become widely available until the late 1970’s and 1980’s. Many of these pearls looked like crinkled rice so were often called “rice krispie” pearls.

By the 1990s, Chinese freshwater pearls were looking smoother, rounder and larger as a result of switching from the cockscomb mussel (Cristaria plicata) to the triangle sail mussel (Hyriopsis cumingii). China was now the largest producer of cultured freshwater pearls, although some were also produced in Japan and the United States. As a result of Chinese competition, the U.S. is no longer cultivating freshwater pearls on a commercial basis.

At the turn of the century, beaded freshwater pearls in the shape of coins, squares, triangles, crosses and other shapes became popular. They were created by inserting a shell bead along with a piece of donor mantle tissue into the mantle of a live mussel. The donor mantle tissue helped form a little pocket around the bead called a “pearl sac” in which nacre was secreted around the bead. The resulting pearls had the same shape as the shell bead nucleus and were often called coin pearls regardless of their shape.

Later the Chinese discovered that they could get a larger flame shaped pearl if after the harvest of a coin pearl, they inserted a round bead into its existing pearl sac and returned the mussel to the water. These flame shaped pearls are also called “fireballs” or second-harvest beaded freshwater pearls.

Akoya, Tahitian and South Sea pearls have always been cultivated by a different method than beadless freshwater pearls. A shell bead nucleus and piece of donor mantle tissue are inserted into the gonad (sex organs) of an oyster instead of into the mantle. About 10–15 years ago the Chinese decided to try growing beaded freshwater pearls in the gonad like saltwater pearls instead of in the mantle. The resulting pearls were rounder than mantle-grown pearls and as large as South Sea pearls but with the same colors as freshwater pearls. Japan Kasumi pearls are also beaded freshwater pearls that are grown in the gonad.

South Sea cultured pearls are saltwater pearls from the silver-lipped & gold-lipped oysters. Indonesia and the Philippines are the biggest producers of pearls in the 9–12 mm range. Australia is the main source of South Sea pearls above 12 mm. Golden South Sea cultured pearls are cultivated in gold-lipped oysters. Most are produced in the Philippines but Indonesia and Australia are also significant sources of golden South Sea Pearls.

Most of the black saltwater pearls on the market are from French Polynesia and are often called Tahitian pearls. Even though most are gray, they come in various colors, but are classified as black pearls since they are cultivated in the black-lip oyster (Pinctada margaritifera). When Tahitian pearls were first introduced to the market, top quality strands consisted of pearls of similar color. However, in recent years multicolored strands have become popular. Many of the pearls advertised as Tahitian pearls on the Internet and at some gem shows are actually dyed freshwater pearls.

Mexican pearls from the rainbow-lipped oyster (Pteria sterna) are also classified as black pearls since they often resemble pearls from the black-lip oyster. They are cultured in Guaymas, Mexico and sold as Sea of Cortez pearls.

When something is prized, it is often imitated and pearls are no exception. Renée talked about buying “real pearls” off the internet for $1.99 and they were even knotted! The most important part for all of us was the easy tests on how to tell if pearls are real or imitation. One easy test is to rub them against your teeth. A real pearl will feel “gritty” whereas fake pearls usually feel smooth. But please do not do this hard, as your teeth are harder than pearls are and you can actually damage the pearls by doing this test.

A better way is to carry a 10x loupe to magnify the surface of the pearl. Imitation pearls generally have a grainy, glittery, pin-point like surface. Real pearls look smoother under 10x magnification and often have characteristic blemishes and drill holes that distinguish them from fake pearls. Angled-in drill holes, and a very thin ragged coating or swirly areas around the drill hole are signs of imitation pearls. Plastic imitations feel light weight, lack overtone colors and are not as cold as real pearls.

Detecting treated pearls such as dyed golden pearls is more difficult than detecting imitation pearls. Magnification can help detect coated pears and some dyed pearls, but hi-tech equipment may be required to identify color-treated pearls. It’s best to get a lab report when buying expensive pearls. In addition, have the seller indicate on the receipt if the pearls are saltwater or freshwater and if colored pearls are of natural color. Assume that white cultured pearls have been bleached unless otherwise indicated.

The last part of Renée’s presentation showed examples of natural oyster and mussel pearls, abalone pearls, melo pearls, conch pearls and clam pearls. In 1917, Cartier purchased their New York building with two strands of natural oyster pearls worth a million dollars at that time. They were resold for $157,000 in 1957, but prices have reversed since then. in 2012, another double strand natural pearl necklace sold for 3.7 million dollars at a Christie’s auction. There has been a renewed interest in natural pearls because of their rarity and as a result, their prices have been increasing.

If you do nothing after attending the meeting or reading this article:  Please learn how to take care of your pearls.  Do NOT use commercial cleaners, ultrasonic cleaners, steam, detergents, toothbrushes or any abrasive.  After wearing them, wipe them down with a damp chamois cloth paying attention to the areas around the cord where oils from the body can hide. Do not hang your pearls, but wrap them in natural cloth (never plastic) and store them in a dark location.  If you wear them often, consider having them re-knotted at least once a year but examine them to see if the cord is stretching or being damaged in any way. Sometimes pearls are strung with gold beads.  Do NOT do this as the gold can discolor the pearls. Take your pearls off when putting on perfume or lotion. Do not shower or swim while wearing them. Check mountings often if pearls are set in a pin or ring mounting. With proper care, pearls can provide you with a lifetime of enjoyment.

Renée’s gem books are available at major book stores such as Barnes & Noble, at the GIA & some jewelry supply dealers and from Internet sellers such as and Additional information about Renée and her books is available at




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