The iridescent lining of an abalone shell is nacre, built from flat aragonite tablets roughly half a micrometre thick, laid down in overlapping layers and separated by thin sheets of protein and polysaccharide. By mass the structure is overwhelmingly mineral, and bulk aragonite is brittle.
Nacre is not. When a crack tries to run through it, the organic layers deflect it along the boundaries between tablets, and tablets slide and lock rather than snapping cleanly. Energy is dissipated across many interfaces instead of concentrating at a single crack tip. Measured work of fracture for nacre is orders of magnitude greater than for the same mineral without the layered arrangement.
That contrast has made nacre a standing model for engineered composites, and layered brick-and-mortar materials imitating it have been made in laboratories. The claim to treat carefully is the leap to products: laboratory analogues have reproduced parts of the toughening behaviour, but nacre-inspired materials are not yet a routine industrial substitute for ceramics.