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Freshwater Pearls vs Seawater Pearls

Cultivation Differences 

Freshwater Pearls

Freshwater pearls are cultivated through the transplantation of the membrane cells of a mussel. The nucleus is typically a small grain of sand or a parasitic organism, and the entire pearl is composed of pearl nacre. The growth period for freshwater pearls is generally 1-2 years. In the pearl trade, non-nucleated cultured pearls are often referred to as "freshwater pearls."

China, particularly Zhuji in Zhejiang Province, is renowned for its production of freshwater pearls. These pearls prefer to grow in relatively enclosed water environments, resulting in less movement of the nucleus and, therefore, lower roundness. China dominates the global production of freshwater pearls, accounting for 90% of the total worldwide output.

Seawater Pearls
Seawater pearls are nucleated pearls, meaning that a nucleus is artificially inserted into the mollusk, and the pearl sac secretes nacre to encase the nucleus. The growth cycle for seawater pearls is typically around 3 years. Internationally famous seawater pearls include Akoya pearls from Japan, Southsea pearls referring to Philippines, Indonesia, Thailand, Myanmar, Australia, and Tahiti black pearls, which are produced in the seawater lagoons of French Polynesia in the South Pacific. These pearls are highly valued and are known for their unique colors and luster. Seawater pearls are typically cultivated in open seawater, where they have access to more nutrients and organisms to nurture their growth.

What are the differences in the pearls produced by the two in completely different cultivation environments and techniques?

Freshwater Pearls

Seawater Pearls

Pearl Luster

Freshwater pearls have a low density. A single freshwater oyster can produce 10-20 or more freshwater pearls, and they can grow from a nucleus-free state to 7-8mm in size within two years. This rapid growth rate results in a relatively loose structure of the pearl layer.

Seawater pearls have a longer growth cycle, higher density, and therefore, they have better luster and a stronger mirror-like effect.

Pearl Layer Thickness

Freshwater pearls are composed of 100% pearl nacre, so the pearl layer is thicker compared to similarly sized seawater pearls.

According to international standards, seawater pearls must have a minimum nacre thickness of 0.3mm in order to be sold.

Pearl Shape

Due to the absence of a central nucleus, freshwater pearls have a tendency to develop various shapes. They commonly exhibit rice-shaped, oval, or button-like shapes, while perfectly round shapes are less common. It is rare to find larger-sized freshwater pearls, making it challenging to achieve the same level of size and roundness as seawater pearls.

Seawater pearls, having a nucleus inside, often have a spherical or semi-spherical shape, such as Mabe pearls. The shape of seawater pearls tends to be more regular, and they can grow larger in size. The probability of achieving a perfectly round shape is higher in seawater pearls.

Pearl Size

Freshwater pearls grow naturally inside the oyster, and as a result, their size cannot be precisely controlled. They can vary in size, ranging from as small as 1mm to as large as 7mm. It is extremely rare to find flawless, perfectly round freshwater pearls larger than 12mm.

Nearly every seawater pearl produced by oysters will have a minimum size that is not smaller than the diameter of its nucleus. Generally, seawater pearls range in size from 6mm to 15mm, with 12mm round pearls being quite common.

Pearl Color

Freshwater pearls encompass a wide range of colors, although some colors are extremely rare. The most common colors for freshwater pearls are white, pink, and purple. Black freshwater pearls commonly seen in the market are typically achieved through dyeing processes.

Natural colors like purple and pink are not typically found in seawater pearls, but peacock green (black) is a unique color found in Tahiti pearls, which are seawater pearls. The highly valuable golden hues seen in Southsea Gold Pearls cannot be accurately replicated by freshwater pearls.

Pearl Blemished

Freshwater pearls commonly have visible ridges or grooves, which can result in a rough texture and a slightly gritty sensation when touched.

Seawater pearls have very few occurrences of ridges or grooves on their surface, even in shallow forms. As a result, they tend to have a smoother and more delicate texture when touched.