Pearl Luster (Teri)

What Is Luster?

“Teri” (luster) refers to the brilliance of a pearl.

In a pearl whose nacre has built up in fine, even layers and whose surface is smooth, the reflection of light produces beautiful interference colors.

Luster is also closely related to “maki” (nacre thickness); generally, the thicker the nacre, the more readily a pearl shows luster.

The luster of a fine pearl is not merely surface shine. You can sense a deep brilliance that seems to well up from within the pearl.

When a pearl with strong luster is worn against the skin, the pearl itself appears to float above the skin, giving off the soft glow unique to pearls.

At Tensei Pearl, we place particular emphasis on “luster” and “nacre thickness,” the indispensable factors in choosing pearls, and our cultivation centers on koshimono.

Comparing Luster

Luster varies from pearl to pearl, and the stronger a pearl’s luster, the higher its rarity value.

It can be difficult to judge by looking at a single pearl, but when several pearls are lined up and compared, the differences become easier to see.

Comparing the figure, you can see that the luster improves toward the right.

As one simple way to tell, the more clearly the round image reflected in the center of the pearl can be seen, the better the luster and the more powerful the pearl.

The Structure of a Pearl

Nacre is made up of numerous calcium carbonate crystals stacked like bricks.

Between those crystals is a protein called “conchiolin,” which acts like an adhesive in forming the nacre.

Each layer of nacre is about 0.4μm (microns) thick, and a pearl is formed by more than 1,000 of these thin layers building up.

Why Pearls Have Luster

When light strikes a pearl, it is first reflected at the surface.

In addition, some of the light penetrates into the nacre and is reflected by each layer as well.

When the nacre layers are fine and regularly arranged, more light is reflected, producing a beautiful luster.

Conversely, when the nacre layers are uneven, light is scattered and the luster becomes weaker.

The condition of the nacre greatly affects the beauty of the luster.

Interference Colors in Pearls

The phenomenon in which two or more light waves overlap in the same place and reinforce or weaken one another is called “interference.”

What occurs in pearls is a phenomenon called “multilayer film interference.”

Depending on how the light strikes, interference colors such as pink and green, like those of a soap bubble, appear.

These interference colors are strongly related to nacre thickness; the thicker the nacre, the stronger the interference colors tend to be.

In pearls with extremely strong luster, a core appears to stand out sharply in the center, and at the same time strong interference colors appear.

In other words, a pearl’s “luster” can be described as the fusion of the brilliance from the reflection of light and the brilliance, seeming to overflow from within, produced by the interference of light.

The Importance of Harvest Timing

When considering pearl luster, one thing that must not be forgotten is the timing of the “harvest.”

Around the time snow flutters over the Yura Peninsula, during the period when the water temperature is at its lowest of the year, Akoya oysters that have stored up nutrients form nacre with a fine crystal structure on their inner surface.

This phenomenon is called “kesho-maki” (finishing layers), and it greatly affects the quality of the pearl.

Kesho-maki makes the surface of the pearl smooth, so that it gives off an even more beautiful brilliance.

Each year, the pearl auctions held by the fisheries cooperative begin in mid-December.

Because Tensei Pearl does not submit pearls to the auctions, we are free to determine the timing of the harvest while watching that year’s water temperature and sea conditions.

When to harvest? That decision requires knowledge of pearl cultivation and many years of experience.

The cultivation techniques developed in this way form the foundation of Tensei Pearl’s pearl making.