Scubaism

Researchers have discovered what makes nacre, the shiny material of pearls and abalone shells, so tough. Commonly called mother-of-pearl, nacre is 3,000 times more fracture-resistant than the mineral it is made of, aragonite.

Using an x-ray technique, the team at the University of Wisconsin-Madison determined the orientation of the crystalline structure within the calcium carbonate “bricks” that make up the material. They found that adjacent bricks can have different crystal orientations, even though their faces are parallel and stack neatly together, as they describe in the 29 June Physical Review Letters.

From their observations, they predict that mineral crystals start growing inside the shell and extend horizontally until they contact another growing crystal and vertically until they hit the overlying mortar. If that crystal contacts another of the scattered crystal formation sites on the next tier up, it should trigger growth of a new crystal with the same crystal orientation, gradually building a rough column of irregular width.

It describes essentially how the abalone lays the “mortar” before filling in the “bricks.”

“If you understand how it forms, you could think of reproducing it, producing a synthetic material that’s inspired by nature - a so-called ‘biomimetic’ material,” said Pupa Gilbert, physicist and research team leader, adding, “If we learn how to harness the mechanism of formation, then we could, for example, produce cars that absorb all the energy at the impact point but do not fracture.”