Pearl Size

Size

For pearls of the same quality, the price generally rises as the size increases.

However, the size of the nucleus used also differs depending on the target pearl size. Therefore, even among pearls of the same size, the value differs between one grown large over time from a small nucleus and one made in a short period with a large nucleus inserted.

Pearl size is expressed as the diameter of the pearl in mm (millimeters).

About Pearl Size

Akoya pearls range in size from approximately 2.5mm to 10mm.

Those exceeding 10mm are extremely rare.

Akoya pearls are generally sorted in 0.5mm increments, and the size is reflected in the price.

South Sea pearls, on the other hand, range from approximately 8mm to 20mm, and they become rarer once they exceed 14mm.

Size and Rarity Value

The most commonly cultivated Akoya pearl sizes are 7mm to 9mm.

Although it varies by year, at the Uwajima first-grade pearl auctions, pearls larger than 10mm account for around 5% of the total.

Among those, pearls of good quality have even greater rarity value.

Also, even for pearls of the same size, the nacre thickness differs depending on the size of the nucleus inside.

Therefore, when comparing pearls of the same size, it can be said that those cultivated over a long time with a small nucleus inserted are more likely to become high-quality pearls than those cultivated in a short period with a large nucleus inserted.

What Is a Pearl Nucleus?

The “nucleus” is the part that forms the core of the pearl.

This nucleus is inserted inside the oyster, and the pearl is formed as layers of nacre build up around it.

Nuclei are mainly made from the shells of a bivalve called “dobugai” (freshwater mussel), which lives in the Mississippi River in the United States, processed into spheres.

The nuclei themselves also vary in quality; those that are close to perfectly round, free of flaws, and without growth-pattern lines or coloring are considered to be of good quality.

Using good-quality nuclei also increases the probability of producing good pearls.

About Baby Pearls

“Baby pearls” are small pearls of 5mm or less.

Among them, those around 3mm are called “sairindama.”

Today, the volume cultivated has decreased, and as they become rarer, prices are tending to rise.

Although they are called “baby,” this does not mean they are pearls that are still growing. They are small pearls cultivated using very small nuclei.

When making a necklace from baby pearls, 100 or more pearls may be used.

For this reason, necklaces using first-grade baby pearls can be expensive.

*There is no clear, unified standard for the size of baby pearls, and standards may differ from company to company.

Why Are South Sea Pearls So Large?

The reason South Sea pearls grow large lies in the type of mother oyster that nurtures the pearl and the difference in its habitat.

South Sea pearls are pearls produced by white-lip and black-lip pearl oysters that live in southern seas.

Among white-lip pearl oysters, those with strong golden pigments produce pearls in waters around Indonesia, the Philippines, Malaysia, and elsewhere.

Meanwhile, those with strong white pigments are produced mainly in the Arafura Sea off northern Australia.

Black-lip pearl oysters are cultivated mainly in Tahiti, and the oyster itself has black pigment.

Water temperatures in these regions are very high, and the mother oysters themselves are several times the size of Akoya oysters.

As a result, they can grow larger pearls than Akoya pearls.