The shell of the red abalone resists breakage due to a brick and mortar structure.

Abalone (Haliotis spp.) build their protective shells in seawater, at low-temperatures, using locally plentiful materials. Their shells are 3000 times stronger than their component parts that are 200% stronger than our toughest high-tech ceramics. These master builders layer elastic organic protein material between rigid inorganic calcium carbonate into a nanoscale "brick and mortar" structure. Any cracks that do form in the shell diffuse in intervening protein layers rather than propagate, a flexibility that makes the shell extremely resilient to breaking. (Courtesy of The Biomimicry Institute)


The shell of the red abalone, Haliotis rufescens, "is an example where nature has used readily available materials (e.g. Ca2+ and CO3-2 ions) in seawater in order to generate a multifunctional composite material. The shell is a ceramic/biopolymer hybrid composite structure with two microarchitecturally different sections. The ceramic component is CaCO3 (in two mineralogical forms constituting the two sections of the shell) and the organic is composed of proteins (and, also, likely to contain lipids and polysaccharides). The outer region of the shell has the prismatic section (P) in which the calcitic (rhombohedral CaCO3: R3m) crystallites are oriented perpendicular to the shell plane. The inner region has the nacreous section (N); here pseudohexagonal platelets (single crystals of microtiles) of aragonite (orthorhombic, Pmmm) are oriented parallel to the shell plane. The calcite crystallites are about a few micrometers in edge, and have an aspect ratio of about 5. The aragonite platelets have a thickness of 0.25– 0.4 micrometers, and an edge length of 5 micrometers (aspect ratio of < or = 0.1!)...While the prismatic layer provides the hardness, the nacreous layer, with alternating layers of aragonite platelets and organic film in between, provides the toughness to the shell. In both regions, the organic constitutes less than 5% by volume of the composites. This results in an "ideal" impact resistant material. (Graham and Sarikaya 2000:145-146)

Journal article
Growth dynamics of red abalone shell: a biomimetic modelMaterials Science and Engineering: COctober 25, 2016
Thomas Graham, Mehmet Sarikaya

Journal article
New classes of tough composite materials—Lessons from natural rigid biological systemsMaterials Science and Engineering: COctober 25, 2016
G. Mayer

Red AbaloneHaliotis rufescensSpecies