How to distinguish pearls

6 factors to distinguish the quality of pearls

Nacre thickness
What forms pearls is a layer of nacre, which is a shell component, on the nucleus. The thicker the nacre gets, the more mature pearls become, then the internal beauty unique to pearls can be seen. The “nacre thickness” is the most important of the 6 factors of pearls. Pearl traders focus on the “nacre thickness” the most. Pearls lacking it are not valued as highly even if the other 5 factors are superb. The nacre is formed inside the mother oysters. Therefore, generally speaking, the longer a pearl stays inside, the thicker the nacre becomes.

真珠層の巻き厚による違い 真珠の断面
There are two types called “Tonen-mono (harvested within a year)” and “Koshi-mono (harvested over the year)”. Koshi-mono has a longer period that pearls stay inside, therefore, nacre become thicker. However, it doesn’t always work that way. It depends on the condition of every Akoya oyster. Weak ones don’t secret nacre so much even if they nurture a pearl more than a year. On the contrary, strong ones secret lots of nacre even within a year. We can’t always say “Koshi-mono” has thicker nacre or “Tonen-mono” has thinner nacre.
光沢 光沢 光沢
“Luster” of pearls has a lot to do with “nacre thickness”. “Luster” specifically means the internal beauty unique to pearls, not just the luster on the surface. When the nacre becomes thick, a pearl can have a rich and deep glitter. So they are highly valued. “Luster” comes from the nacre thickness and the crystal component forming the nacre. The way for beginners to distinguish the luster of pearls is to see how much it can reflect your face just like a mirror. The ones with high quality always reflect figures as well as mirror, but furthermore, you can see how fine the reflection is. Imagine the resolution of digital cameras. The higher resolution a camera has, the finer a picture is. Likewise, pearls with high quality can reflect figures finer on their surface.

In the picture on the left you can see the yellow plush toy that is Ehime Prefecture’s image-up character “Mikyan” on the surface of the pearl. The surface of a pearl with a strong luster is like a mirror.

“Blemish” is a swell or a dent on the surface of pearls. Pearls are formed by a creature, so it’s common that there is a swell or a dent on the surface. When we process pearls, we make a hole near the blemish so that it’s not so obvious. However, blemish can be more than one. We try to make them not so outstanding as much as possible. If blemish is too conspicuous, it can’t be processed as a product. Small blemish can be covered if there is a fine glitter and reflection on the surface. Especially when you choose necklace, the ones with stronger glitter are recommended if you don’t mind comparatively small blemish.
真珠のエクボ 真珠の突起
There are various colors such as pink, white-pink, white, blue, gray, cream and gold. The color is generally categorized into “pink” “white-pink” and “white” in the simple method.
干渉色と実体色 干渉色によって変わる色
“body color” and “overtone”
To categorize it even further, there are “body color” and “overtone”. When you look at a pearl closely, you see different colors on its center and surface. The color on its center is called “body color” whereas the one on the surface is called “overtone”. “Overtone” is a color formed by the layer of nacre. “Overtone” is classified into 2 colors, pink and green.
The left picture is a comparison of how to see. Both pearls’ “body color” and “overtone” are pink, but pearl on the right is the strong overtone. In this way, the pearls with strong overtone shine very much when worn on the skin.
Blue pearl
Blue pearls are categorized into “natural blue” and “cobalt blue”. “Natural blue” literally means a natural color. “Cobalt blue” is the one artificially processed and changed the color. We don’t harvest so many natural blue pearls, they are therefore rare and highly valued.
Gold pearls
Gold pearls can be nurtured from Akoya oysters, but it’s very rare nowadays.
Shell color and pearl color
A part called nacre that we can see inside Akoya oyster’s shell is very beautiful. The color varies pink, white, blue and yellow. The glitter and the color of the shell are reflected on pearls. That’s why pearls vary in color. You never know what color a pearl has until you open the shell. This is the moment of astonishment.
Pearls harvested from Akoya oysters are generally 7mm to 8mm. The ones more than 8mm are considered as large-size. The size of pearls is determined by the size of nucleus inserted in Akoya oysters and the thickness of nacre layered on it. If the nucleus is small, we get a small pearl. Likewise, if the nucleus is large, we get a large pearl. A nucleus is a source of pearl. A round-shape piece of a thick part of the shell called “swan mussel” is used as a nucleus.
What forms pearls is a layer of nacre, which is a shell component, on the nucleus. The nucleus made of shell is compatible with Akoya oysters so that they can nurture pearls and we can process them easily. The size of pearls currently produced in Uwajima is mainly 8mm. Sometimes we can get 9mm pearls, but it is very rare to get pearls bigger than 10mm. If the quality is the same, larger ones have higher value. However, the value of pearls is mainly determined by the nacre thickness. If the nacre is thin, it has no value because it just means the nucleus is big.
Pearls have a variety of shapes. The ones with a perfect spherical shape are certainly highly valued, but it doesn’t mean the ones with an irregular non-spherical shape have no value. Irregular shaped pearls called “baroque pearls” or snowman-like shaped pearls called “Twin” are highly appreciated by fancier.
ツインの真珠 真珠層
Occasionally, we see pearls exactly shaped like a snowman. We call them “Twin”, and they really look like a snowman. When producing pearls, we normally insert one nucleus in one oyster, but we sometimes insert two nuclei depending on the size of the oyster. We call it “Niko-ire (inserting two nuclei)”. When we do this, we make sure to place them apart to avoid the joint. However, they sometimes come out together. Despite the fact that we purposely insert them apart to avoid the joint… How about keeping the “Twin” pearl as your matchmaking charm?

“Baroque pearls” often have a high quality. The irregular shaped pearls called “baroque pearls” basically have thick nacre. What forms a pearl is a layer of nacre. The thickness of one layer is about 0.3µm. Thousands of the nacre layers form a pearl. There is no wonder a pearl can be deformed especially when we think about how many thin layers are piled. When the warp is notable, they become baroque pearls. In other words, the ones with warp have thick nacre. Since the nacre is thick, it has a strong luster.

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798-0102, Japan
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