sciencehabit writes: The windowpane oyster sports a shell so transparent and durable that some Indian and Philippine cities use the coverings as an affordable alternative to window glass. Yet windowpane oyster shells are made up of 99% calcite, a usually brittle material, with a small amount of organic material. A team of researchers wondered how the shellfish’s fingernail-thick armor could survive multiple blows while remaining transparent, a feat unmatched by humanmade materials. When forcefully jabbed with a diamond, the windowpane oyster shell resists shattering by dispersing 10 times more impact energy than raw calcite, the team reports . Peeking at the shell’s crystal structure using an electron microscope, the researchers discovered the oyster’s secret. When stressed, the shell’s crystal structure twists symmetrically, causing an atomic reorganization that forms a boundary quarantining any fractures that might form. This process, called deformation twinning, dissipates energy horizontally and allows the shell to survive multiple hits. The researchers say their work provides a natural template for developing sturdy, transparent materials for windshields and even see-through military armor.