Size as a

Value-Add for Pearls

 

"Do you have 13mm Akoya pearls?"
Even if a customer asks us this question, our answer is always the same.
"Unfortunately, we do not."
Strictly speaking, "it's not impossible for Akoya pearls of that size to exist, but they are extremely difficult to obtain. Even for us, who have been involved with pearls for a long time, we have never seen that size, so this is all we can say."

Now, I would like to discuss pearl sizes, touching upon the mother-of-pearl of cultured pearls and their production, to explain what sizes are available.

 

Size of the Mother-of-Pearl

The size of a pearl is proportional to the size of the mother-of-pearl that produces it.
When cultivating pearls, a spherical nucleus made of shell and a piece of the shell's mantle tissue, called a "piece," are inserted into the shell. The nacre layer then forms around the nucleus, creating the pearl.

This means that larger shells can accommodate larger nuclei, allowing them to produce larger pearls. Conversely, smaller species of mother-of-pearl will inevitably produce smaller pearls.

From left: Akoya shell, black-lipped oyster, white-lipped oyster (gold-lipped), white-lipped oyster (silver-lipped) *Akoya shell is not shaped, others are.

A "nucleus" made by grinding freshwater shells into a spherical shape, serving as the base for cultured pearls. It is inserted into the shell according to the desired size.

 

Sizes in Production

Please refer to the image below.

The size chart in this image shows the main pearl sizes available in the market that we typically handle.
While there are other sizes not listed in the image, their production volume is very small, so we have omitted them here.

■Akoya Pearls
As can be seen from the comparative image of shell sizes, Akoya pearls, which come from Akoya oysters (scientific name: Pinctada Fucata Martensii), are the smallest among cultured saltwater pearls.
They are cultured in sizes from about 3mm to 10mm, with the majority of the total production being 7mm to 8mm in size.
Small sizes under 6mm account for less than 20% of the total production, and especially sizes of 3mm to 4mm, called Rinju, account for only less than 1% of the production.
Large sizes of 10mm and above are also produced in small quantities, and sizes larger than 11mm are rarely produced because they place a heavy burden on the small Akoya oysters.
Therefore, the 13mm size mentioned as an example earlier is basically an unculturable size for Akoya pearls.


■Tahitian Pearls
The next largest size is produced by black-lipped oysters (scientific name: Pinctada Margaritifera), yielding "Tahitian pearls."
The size of the shell is between that of the Akoya oyster and the white-lipped oyster, and cultivated sizes range from about 8mm to 14mm.

The main production ranges from 9mm to 10mm. For sizes larger than 12mm, the yield of pearls with the deep colors characteristic of Tahitian pearls decreases, and lighter-colored pearls become more prevalent.
Therefore, large pearls with deep colors fetch a higher market value.
Currently, small-sized Tahitian pearls are not being cultivated.

■South Sea Pearls (including Golden Pearls)
The largest sizes are produced by white-lipped oysters (scientific name: Pinctada Maxima Jameson), yielding "South Sea pearls."
The shells are large, with a diameter of 20cm or more, and are divided into two types: "silver-lipped" and "gold-lipped," which differ in the color of the nacre along the shell's rim.
Silver-lipped oysters produce white, silver, and cream-colored pearls, while gold-lipped oysters produce gold, yellow, and cream-colored pearls. As they are produced in different areas, they are categorized as different types of pearls.

Both typically produce pearls of 10-11mm, which is an average size for South Sea pearls, whereas it would be a maximum size for Akoya pearls.
Due to the larger size of the shells, the range of culturable sizes is wide, and pearls larger than 15mm, which are rarely seen in Akoya or Tahitian pearls, can be found.

 

How Sizes are Classified

When we classify pearl sizes, we use special tools found only in pearl shops.

One tool is called a "sieve," which uses interchangeable plates with holes of different sizes. These plates come in four sizes within a 1mm range, with 0.25mm increments. For example, for 9mm, there are "9," "9¼," "9½," and "9¾."

Especially when sorting Akoya pearls, these 0.25mm increments are very important. When pairing pearls for earrings, we always use the 1/4 plate.
For example, even within a batch designated as 8-8.5mm, if an 8mm pearl is paired with an 8.49mm pearl, there will be a noticeable difference in size. Therefore, we use the "8¼" plate to separate them into 0.25mm increments (8-8.25mm and 8.25-8.5mm) to create pairs with the smallest possible size difference between the left and right.

Furthermore, unlike Tahitian and South Sea pearls, Akoya pearls are traded in 0.5mm increments. Therefore, farmers (producers) also use "sieves" to sort and display their pearls by size.
This tool, known as a "sieve," is one of the most indispensable tools in the pearl business.

 

Another indispensable tool is the "gauge," used for measuring sizes, capable of measuring in 0.01mm increments, making it extremely important.
After separating pearls into 0.25mm increments with the "sieve," this "gauge" is used to measure even finer sizes.

For instance, when assembling an Akoya pearl necklace, it is preferable to use the largest pearl for the center bead, making "gauge" measurement essential. It is also an indispensable tool when creating jewelry designs that require specific numerical verification, such as the size of pearls that can be affixed to a ring.

 

Choosing Pearls by Size

When determining the value of a pearl, "size" is a significant factor.
Naturally, the larger the size, the higher the market price. If other factors such as pearl shape, luster, extent of flaws, and color also improve in grade, the price will rise accordingly.

However, knowing the typical production size for each type of pearl can help you choose pearls wisely.

For example,
If you want a "beautiful, large white pearl," Akoya pearls of 10mm or 11mm are rare and expensive. However, for South Sea pearls, 10mm or 11mm are average sizes, making them more affordable than Akoya pearls of the same size (depending on the grade being compared and the market price at the time of consideration).

Also,
If you want a large Tahitian pearl with a deep color, those over 12mm with deep colors are scarce and become very expensive. Therefore, if you prioritize good quality at an affordable price, you might choose a 10mm or 11mm pearl with a deep color.
By understanding these options, you can choose pearls more effectively.

If you have an ideal pearl in mind, we hope this discussion will be helpful.

At sCenes, as a brand specializing in pearls, we provide extensive knowledge and information about pearls.
If you have any requests such as "I want a pearl like this," please feel free to contact us anytime.

 

We filmed the process of "sorting pearls" with a sieve.
It's a short video, so please take a look if you have time.

※Please set the video quality to 1080p in the Youtube playback settings.