Understanding Pearls

Published On: 
February 18, 2022
Japanese Pearl Oyster pearls.jp tokyo japan

Understanding Pearls

by pearls.jp | Tokyo, Japan.

Part 1


We at Pearls.jp believe that helping our customers understand pearls is key in appreciating the quality of pearls. It is part of what we go over in our pearl academies (in Tokyo, Japan), that we give to anyone who is passionate or interested in pearls.

In this post we will be discovering how pearls are formed and later envision what determines its beauty to give our readers a better understanding on the world of pearls. Main topics we will cover:

  • What are pearls?
  • How are pearls formed (natural and cultured pearls)?
  • What to look for in a pearl (what is a good pearl)?
  • Pearl Pricing

How are pearls formed (natural and cultured pearls)?

Some people would say that a pearl is a precious gemstone and leave it at that. Some may think that it is a work of art and beauty which mother nature had provided. But most would not have considered that it is the one and only gemstone that comes from a living creature. Oysters, and mussels produce pearls. In scientific terms, mollusks under the class animalia have the capability to produce pearls. This includes abalone, marine shells, clams, mussels, and oysters.  Pearls come in various shapes, size, luster and color. The type of pearls found vary depending on what type of mollusks created the pearls. Commonly, saltwater pearls are found in oysters, while freshwater pearls are often produced by mussels.

In some myths, sand is thought of to be the substance that forms into pearls, which is inaccurate. In reality, pearls are formed by the presence of foreign particles inside the shells of mollusks. Naturally this is quite a rare process which is why it is estimated that only 1 in 10,000 naturally occurring oysters produce pearls. And as you might have assumed, back in time before human beings learned how to culture pearls, they relied on naturally occurring pearls which led to over harvesting of oysters and diminishing its overall presence in the world. Which is why naturally occurring pearls are extremely rare. Since then we discovered how to initiate the process of pearl growth which helped meet the high demand for pearls.

Japanese Pearl Divers

Nowadays, pearls are grown under controlled environments and as a result of human interference. This process is called Pearl Culturing. This is the main difference between natural and cultured pearls. When a foreign object is introduced inside of a pearl, which in the case of cultured pearls is done by inserting a nucleus into an oyster. The oyster forms a crystalline substance and coats the foreign particle. This substance is called ‘nacre’ is a combination of calcium carbonate and protein which makes it tough and lustrous - and something beautiful to look at.  This substance after 6 months to 4 years when it becomes mature is what we know to be pearls.

What to look for in a pearl (what is a good pearl)?

To simplify the process of understanding pearls we defined the 5xS system which refers to:

  1. Shine (luster)
  2. Shape
  3. Size
  4. Shades (colors and overtones)
  5. Surface

Shine (Luster)

This characteristic in pearls is what makes it very desirable. It is in-fact what pearls are all about because the beauty of the pearl is defined by its level of shine. The luster means how well the pearl reflects and breaks the light. This is what creates the pearlescent effect that results in beautiful color overtones and depths.

AAA Grading System (what does AAA mean?)

It is a way to compare pearls depending on their luster. It is used by retailers to define and compare its luster. It is important to remember that often, retailers try and define the entire quality of a pearl into AAA, AA, A and so on. This doesn't do justice to the pearl or the customer as it ignores many other factors that define the quality. As an educated buyer you will want to learn as much as possible about the pearls you are getting.

Grading pearls by luster

Japanese Akoya Pearl Strand AAA


Pearls can be found in a variety of shapes. Contrary to human expectation, perfectly round pearls are quite rare to find. There are so many factors that affect the shape of the pearl starting off with the nucleus which acts as a guide in forming the shape or simply the positioning of the pearl inside the oyster which might create a flatten pearl if left against the shell. Pearls come in many shapes such as round, button, drop, ovals and baroque shapes.


Pearls are measured in sizes ranging from 2mm to 20mm and up. Akoya pearls are often the smallest of all pearls, reaching 9~10mm at most. while South Sea and Tahitian pearls are the larger pearls starting from 8mm. Size of the pearl also helps determine the value of the pearl. Larger the size of the pearl, the more expensive it is expected to be. The size is effected by the type of pearl (and the type/size of oyster it grows in) as well as the nucleus' size and time it grows.

Shades (colors and overtones)

Pearls come in a variety of overtones. Most Akoya pearls have pinkish and silverish hues. Tahitian pearls (black pearls) often have grayish, dark greenish, shiny black or peacock hues. The variety of overtones are due to light being reflected from the layers of nacre in the pearl. South sea pearls are either white or gold, and within these colors can be deep or light. The south sea white pearl is often cooler than the Akoya pearl.

Japanese Akoya Hanadama Pearls


As pearls are natural gemstones, they have natural imperfections. The "cleaner" pearls are the more expensive they get. Imperfections can be spots, simples, or rough skin (that just doesn't look that smooth). This is also a price determining factor.

Pearl Pricing

A pearls value is determined by its rarity. So basically, a larger pearl will cost more than a smaller pearl (holding other factors such as luster equal). A round pearl will cost more than a baroque pearl and so on. However, this does not necessarily indicate a pearls quality. Actually, we would argue that luster is the only characteristic that is ubiquitous. All the rest are a matter of personal preference. Some people do not mind blemished pearls, and actually prefer them as they give the pearl "character", some may prefer smaller pearls. What we saw in our years in this business is that a pearl ends up being an extension of a persons' character and they will always end up buying the pearl that reflects themselves the best. And that in our opinion is the beauty of pearls. The fact that every pearl is unique, reflects on whoever is wearing them. While price may reflect a pearls rarity, it doesn't mean its "better" necessarily.


By going over what pearls are and discovering their features, we have come to the end of the first part of “Understanding Pearls”. In the second part we will be address the various types of pearls, and this will help the readers find what type of pearls are most suitable for themselves or their loved ones. Stay tuned.

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