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Home > Pearl knowledge



1- How are pearls formed?

2- What is and how is a ‘cultured’ pearl formed?

3- What are Keshi pearls?

4- What are ‘Shell’ pearls?

5- Main types of cultured pearls

6- Why do saltwater pearls and freshwater pearls have vastly different prices?

7- Why do pearls have different sizes?

8- Why do pearls have different shapes and colors?

9- South Sea pearls characteristics

10- Tahitian pearls characteristics

11- Akoya pearls characteristics

12- Common misconceptions about pearls

13- Care and maintenance of your pearls

14- When should I restring my pearl necklace?

15- Did you know that…?


1- How are pearls formed?

When a foreign organism finds its way inside an oyster, the oyster protects itself by secreting a layer of calcium around that organism to isolate it. That layer turns solid and forms the first layer of pearl ‘nacre’. Once that process is initiated, the oyster keeps producing layer after layer of nacre around that core, and that becomes what we call a pearl, and this is how a pearl is made in the ‘wild’. In the pearl trade, these ‘wild’ pearl are referred to as Natural pearls (as opposed to ‘cultured’ pearls, as described below in section 2). If we were to cut a pearl in half and look at it under a microscope (or even a high power loupe) you could actually see these layers. The combined color and luster (the shine) of these layers of nacre is what we actually see as the ‘color’ and ‘luster’ of a pearl.

2- What is and how is a ‘cultured’ pearl formed?

With the exception of the ‘core’ of a pearl as described above in section 1, a cultured saltwater or freshwater pearl is formed exactly like a pearl in the ‘wild’. The difference with a cultured pearl is that the core that stimulates the oyster to produce the layers of nacre around it, has been inserted inside the oyster by the pearl farmer. From then on, the oyster is put back and cared for in the ocean, or in the lake in the case of freshwater pearls. A cultured pearl is basically a pearl that has been ‘cultivated’ and then harvested from oysters from pearl farms in the ocean or lakes. This is somewhat similar to fish that are farmed and cared for in ocean and lake farms too.

The ‘core’ of a cultured pearl is called a nucleus, and the process itself is called the nucleation of the oyster. Today, nucleation is done sometimes by pearl farmers themselves, but often by trained technicians whose specialize in that process.

The nucleus of a saltwater cultured pearl is a round solid bead usually made from Mississippi river shells, whereas the nucleus of a freshwater pearl is a piece of the mantle tissue cut from an actual pearl producing mussel. Therefore both saltwater and freshwater pearls that come from pearl farms are cultured pearls. A common misconception about freshwater pearls today is that they do not have a nucleus, and that is only because the mantle tissue that was inserted as a nucleus in the freshwater mussel has already decayed inside the pearl. If we were to cut a freshwater pearl in half, we would find a slightly hollow center, whereas in the case of saltwater pearls (i.e. South Sea, Tahitians and Akoya pearls), the center is of course the solid Mississippi shell bead.

(Also, please refer to section about common misconceptions about pearls and pearl imitations.)

3- What are Keshi pearls?

True keshi pearls are pearls that have not been nucleated by human intervention. Keshi is actually a Japanese word that refers to natural (i.e. wild) pearls as opposed to cultured pearls (as described above in section 1 & 2).

Historically, Keshi pearls came mostly in very small sizes and shapes (mostly 1 to 2mm) from Japanese Akoya shells, and thus acquired the term ‘seed’ pearls in the U.S.A. Today, Keshi pearls come also in much bigger sizes (and sometimes in super rare jumbo sizes), because South Sea and Tahitian shells are much bigger than Akoya shells. Typically, Keshi pearls are not round but mostly freeform (baroque shape), with round pearls being the rarest of the rarest of pearls.

Misleading advertising and misinformation abound around keshi pearls. One will find common (cultured) freshwater pearls readily advertised as Keshi pearls on internet sites and other. The fact that common (cultured) freshwater pearls have a nucleus that has decayed at their center (and therefore, the claim of ‘no’ nucleus at their center), is at the heart of this matter. The other major misleading information is about baroque (freeform/non round) shape pearls. Both saltwater and freshwater baroque shape cultured pearls are sometimes advertised, marketed and sold as keshi pearls. The typically freeform shape of Keshi pearls is the cause of this matter.

4- What are ‘Shell’ pearls?

Shell pearls are not pearls, and they did not come out of an oyster or any ‘shell’. Today, there are many types of pearl imitations being sold under many different names and labels; Shell pearls are one of these. They are beads made in a factory from ground up shells, coated with a synthetic color dye and a top coating of a synthetic varnish to give shine and luster. Typically, with time, these synthetic coatings will peel.

(Please refer to section about common misconceptions about pearls and pearl imitations.)

5- Main types of cultured pearls

There are 2 main types of cultured pearls today, saltwater cultured pearls produced in various oceans around the globe, and freshwater cultured pearls produced in lakes. Saltwater pearls are the South Sea pearls, Tahitian pearls, and Japanese Akoya pearls. South Sea pearls are mainly produced in Australia and Indonesia. Tahitian pearls are produced in French Polynesia while Akoya pearls are mainly produced in Japan. Freshwater pearls are basically produced in China.

Saltwater oysters produce only one pearl at a time. Typically, one saltwater pearl is harvested after about a year and a half to two years. On the other hand, freshwater pearl shells can and commonly produce 10 to 20 pearls per shell, although this also depends on the size of the nucleus and pearls being produced; most freshwater pearls are commonly harvested in about six to eight months.

6- Why do saltwater pearls and freshwater pearls have vastly different prices?

They have vastly different prices for two main reasons. First, saltwater pearls are (very) rare compared to freshwater pearls. The second reason is that, for the last 25 years or so, freshwater pearls have lost some value and declined in price.

One can compare price differences between saltwater cultured pearls and freshwater pearls to the price of platinum versus silver, for example; while both are precious metals, both white and lustrous, platinum is multiple the price of silver.

(Please refer to section about common misconceptions about pearls and pearl imitations.)

7- Why do pearls have different sizes?

There are two main reasons why pearls come in many completely different sizes.

Pearl producing oysters and shells are vastly different in physical size and therefore they are limited to how large of a pearl they can produce. For example, the largest is the white lip South Sea shell which can grow as large as a dinner plate! Second largest is the black lip Tahitian shell which can grow to about 7” in diameter. And last but not least, is the Akoya shell which can grow to about 3” in diameter. The biggest of Akoya oysters can only produce up to 9-10mm pearls, and these would be considered jumbo and rare size pearls. On the other hand, that same 9 to 10mm size would be considered a regular size for Tahitian and freshwater pearls, and a smaller size for South Seas.

The size of the nucleus of a pearl is the other main reason why pearls are produced in different sizes. A larger oyster is typically nucleated with a larger nucleus to produce a larger pearl.

Other common factors that affect pearl size are how long the farmer keeps the oysters in the water before harvesting them (ideally, 18 to 24 months). Nutrients in the water also affect the health of the oyster and therefore the size and quality of the pearl it produces.

8- Why do pearls have different shapes and colors?

All pearl producing oysters and shells produce pearls of different colors and shapes.

The shape of a pearl is the natural shape of the pearl at harvest. The shape of a pearl is not ‘cut’ like precious stones and diamonds, for example. The main shapes of pearls are round, oval, button, (tear)drop and baroques (freeform). The proportion of shapes to each other varies from one pearl farm to another. Pearl farmers and cultivator strive to produce the roundest pearls possible, because round pearls command higher prices. The reason oysters produce non round pearls is because, the ‘womb’ where the pearl grows is not perfectly round. Nucleation technicians strive to put the nucleus at the best spot in the oyster.

As for the colors of pearls, different oyster strains can naturally produce pearls with only a certain number of colors. The rarity and quantity of these colors is one of the main factors that ultimately affect the price of these pearls. In contrast to diamonds which have one single color, pearls have almost always secondary overtones; for example, a white South Sea pearl can have a metallic overtone, or a black Tahitian pearl might have a distinct green overtone. Certain combination of color/overtone and especially their intensity are very rare. These are the equivalent of colored diamonds; for example a yellow diamond is rarer and rarer as it has a more and more intense and vivid yellow color. Some of these colors are described in the following sections.

9- South Sea pearls characteristics

South Sea pearls are mainly produced in Australia and Indonesia.

South Sea pearls are the classic large white to champagne and gold color pearls. Their color actually extends from the white to the silver and slight grey overtones, and from the white and off white to the champagne cream color, and of course to the golden at their deepest. Sometimes South Sea pearls come in rare color hues such as ‘sky’ blue or light ‘pistachio’ colors, and it’s the depth and intensity of these colors that makes them rare or common (just like colored diamonds, actually). Pearls come in many different shapes, from the perfectly round to oval shape, tear drop shape and freeform baroques. They range in size from about 8mm to approximately 21mm, although the most common sizes are 9mm to 16mm, with 17mm and up considered the jumbo and super jumbo sizes. South Sea pearl strands are usually graduated in size; Straight size necklaces are less common, especially in the larger sizes.

10- Tahitian pearls characteristics

Tahitian pearls are produced in French Polynesia.

Tahitian pearls are the classic ‘black’ pearls. Their color range actually extends from black to grey, to the silver colors, often with secondary color hues (referred to as overtones) of green, blue and bronze. Sometimes Tahitian pearls come in rare and fancy colors such as turquoise or bright pistachio among others. The rare combination of two rare colors and color overtones are a wonderful aspect of Tahitian pearls too. Just like South Sea pearls, Tahitian pearls come in many different shapes, from the perfectly round to ovals, drops and free forms baroques. They range in size from about 8mm to 19mm, although the most common sizes are 8mm to 15mm, with 16mm and up considered the jumbo and super jumbo sizes. Tahitian pearl strands are usually graduated in size; Straight size necklaces are less common, especially in the larger sizes.

11- Akoya pearls characteristics

Japanese Akoya pearls are the classic white pink pearls, also commonly known as ‘cultured pearls’. This is a generic name really, since 99.99% of all pearls, saltwater and freshwater alike, are cultured. Sometimes, they are referred to as ‘Mikimotos’ which is actually a brand name rather than a type of pearl.

The white pink color is the one that is instantly recognizable by most as an Akoya pearl. Akoya pearls come actually in many colors (and secondary color hues) such as pink, white, and the rarer silver, grey, champagne, gold and extremely rare blue color. Akoya pearls too come in many different shapes, from the perfectly round to ovals, drops and free form baroques. Akoya pearls range in size from about 2mm to 10mm, although the most common and popular sizes are 6.5mm to 8.5mm. Usually Akoya pearl strands come in calibrated (i.e. straight) sizes with increments of 0.5mm, i.e. a strand will be from 6-6.5mm, or from 6.5-7mm, etc… Akoya pearl strands sometime come in graduated sizes.

12- Common misconceptions about pearls

Keshi Pearls: The term ‘Keshi pearls’ is one of the most misleading and uninformed in the advertising and marketing of pearls today. True keshi pearls are pearls that have not been nucleated by human intervention. One will find common cultured freshwater pearls readily advertised as Keshi pearls on internet sites and other. The fact that common cultured freshwater pearls have a nucleus that has decayed at their center (and therefore, the claim of ‘no’ nucleus at their center), is at the heart of this matter. The other major misleading information is about baroque (freeform/non round) shape pearls advertised as keshi pearls. Both saltwater and freshwater baroque shape cultured pearls are sometimes advertised, marketed and sold as keshi pearls. Although true keshi pearls are typically baroque in shape, many cultured pearls too, in both saltwater and freshwater come in these same baroque shapes also. Please refer to section 3 above for more info on true keshi pearls.

The price and value of pearls varies tremendously based on origin and status of the pearl. As a matter of fact, saltwater keshi pearls are much, much rarer than almost any freshwater pearl. True saltwater keshi pearls are also much rarer than any baroque pearls, saltwater and freshwater alike. When buying true keshi pearls, one must be certain of these two above facts first and foremost.

Dyed freshwater pearls vs natural color Tahitian pearls: Since Chinese freshwater pearls commonly come in the same sizes as Tahitian pearls, Chinese freshwater pearls are commonly dyed various shades of black, dark greys and other to imitate the color of true Tahitian pearls.

Shell pearls: these are not pearls, but a pearl imitation product made from ground up shells, that is coated with synthetic layers of color and varnish. Please refer to section 4 above for more info.

Cultured pearls vs cultured stones: Cultured pearls are the natural product of oysters that have been cared for in ocean and lake farms, whereas cultured stones (cultured diamonds, cultured rubies and countless others) are lab created products.

13- Care and maintenance of your pearls

The care and maintenance of your pearls is very easy. Pearls are softer than mineral gemstones and require a bit more care. They are affected by alcohol and other ingredients contained in hairspray, perfume, cosmetics, etc…; so put on your cosmetics first and your pearl jewelry last. Pearls can also be affected by other chemicals, such as detergent when washing dishes, shampoo when taking a shower, or chlorine in the swimming pool or spa. Although pearls are not easy to scratch or chip, do store your pearls in a soft pouch separately from your non-pearl jewelry, since scratches cannot be fixed like scratches on gold and other metals.

Cleaning your pearls is easy. Wipe your pearls a couple of times with a soft cotton cloth to remove traces of cosmetics or other. Never use ultrasonic cleaners or chemicals or solvents that are routinely used to clean gold, silver and other jewelry metals.

14- When should I restring my pearl necklace?

You should send your pearl necklace for restringing when the pearl between the two knots is too loose, or when parts of the thread are frayed. In general, pearls are restrung with silk thread and individually knotted for added security.

15- Did you know that…?

Did you know that Mikimoto Pearls (registered trademark) is actually a brand name and not a type of pearl?

Did you know that in 1916, Jacques Cartier bought his 5th Avenue store by trading 2 pearl necklaces for the land?

Did you know that June is Pearl month?

Did you know that Pearls: The only Gemstone from a living creature?

Did you know that pearls are the only gemstones made by a living animal?

Did you know that harvesting a pearl does not kill the oyster as it can be implanted again to produce another pearl?

Did you know that the scallops of pearl oysters are edible? They are actually considered a delicacy that is available only when pearls are harvested. Typically, these are consumed by the pearl farmer, his immediate and extended family. These scallops almost never reach commercial markets because most pearl farms are located far away from larger cities and towns.

Did you know that many pearl oysters used for pearl production are also raised alongside pearl

bearing oysters? If only wild oysters were to be used, certain types of wild oysters would be

quickly depleted!!!

Did you know that a very large proportion of pearl farms are small, family run businesses?

Did you know that you cannot transport/transplant certain type of oysters from one area of the

globe to another because they will not survive local water conditions?