The Unique Structure and Properties that Make Pearls So Precious

Pearls are a gem formed within the soft tissue of certain mollusks.

When an irritant like a grain of sand gets inside the mollusk’s shell, the mollusk secretes layers of nacre around the irritant, slowly forming a pearl over time. This is why there is an expression “old oysters produce pearls” in Chinese.

Pearls have a concentric ring structure with radial pearl layers. The interaction of light on these radial layers produces an iridescent luster known as the pearl’s orient.

Pearls are generally spherical or near-spherical in shape. Due to their layered structure (average 1000 layers per 0.5mm), they have good toughness and elasticity. Tests show they can bounce up to 70% of their drop height when dropped from 20cm, much higher than a sphere of similar size and different composition. This can help distinguish real pearls from faux pearls made of glass or resin.


  1. Color: light (pink, white), colored (red, green, golden yellow), black (purple, blue, black). Combination colors of pink, blue and green are produced by light interference and diffraction through the transparent layered structure on the pearl’s surface.
  2. Transparency: semi-transparent to opaque.
  3. Luster: ranges from translucent to opaque, depends on the thickness of the pearl layers, arrangement of layers, transparency and surface texture.
  4. Density: saltwater 2.61-2.85 g/cm3, freshwater 2.66-2.78 g/cm3.
  5. Refractive index: 1.53-1.56, related to the smoothness of the pearl’s surface.
  6. Fluorescence: Black pearls show weak to medium reddish-orange fluorescence under longwave UV. Other colored pearls show weak to strong fluorescence in light blue, yellow, green or pink.
  7. Other: Bubbles when exposed to acid, turns brown when overheated.
  8. Visible structure: Concentric layered radial structure, surface growth lines.


Hello, my name is Yang. I'm from China. I'm a freshwater pearl farmer who wants to share more of these beautiful gems with people worldwide. I grew up learning my family's time-honored cultivation methods. Now I supply high-quality freshwater pearls and pearl jewelry. Please feel free to contact me if you'd like to learn more about my pearls. I look forward to connecting with fellow pearl enthusiasts!

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