Few composites forged by nature are as tough as pearls, and now scientists have finally figured out how the tiny layers of this pearlescent substance make them so strong.

The intrinsic strength of pearls lies in their molecular structure. Pearls are primarily composed of calcium carbonate in the form of aragonite, a crystalline substance.

The layers of aragonite crystals are arranged in a microscopic, overlapping pattern. This arrangement creates a solid structure, providing pearls with their impressive toughness.

Nacre, also known as mother-of-pearl, is the substance that forms the luminous coating of pearls. It is secreted by mollusks in response to an irritant such as a grain of sand or a parasite invading their soft tissues. Over time, the mollusk coats the irritant with layers of nacre, resulting in the formation of a pearl.

The unique layered structure of pearls contributes to their resilience. As the mollusk secretes nacre, it forms concentric layers around the irritant, gradually adding thickness and strengthening the pearl. These layers interlock tightly, providing a protective shell that is resistant to external forces.

Surprisingly, the pearl layer did not lose any resistance during compression. Tests have shown that the level of elasticity of the pearl layer does not decrease even under repeated impacts up to 80% of the yield strength. Pearls possess a relatively high hardness on the Mohs scale, typically ranging between 2.5 and 4.5.

Although not as hard as some gemstones, such as diamonds or sapphires, pearls exhibit excellent scratch resistance. This allows them to withstand daily wear, reducing the risk of surface damage and maintaining their lustrous appearance over time. Unlike gemstones, which are created through geological processes, pearls are products of living organisms. This organic origin contributes to their natural resilience.

Pearls also possess certain natural deterrents that contribute to their toughness. The outermost layer of the pearl called the periostracum, acts as a protective covering against environmental factors and potential harm. This thin layer, composed of organic materials, shields the underlying layers, helping to preserve the integrity of the pearl.

Although pearls are inherently durable, proper handling and maintenance are still essential to preserve their toughness. Minimize exposure to harsh chemicals, extreme temperatures, and excessive humidity, as these factors can potentially weaken or damage the nacre layers. Gently wiping pearls with a soft cloth after wear and storing them separately from other jewelry can help maintain their resilience and prevent scratches.