Compositional and structural variations at various scale levels have been investigated in the shells of the modern brachiopod Megerlia truncata combining transmission electron microscopy (TEM), cathodoluminescence (CL), laser-ablation-inductively-coupled-mass-spectrometric (LA-ICP-MS) and micro-Raman spectroscopical (µRS) analyses. Our results show that these shells can be addressed as hierarchially structured, multi-scaled organic/inorganic fibre composites. A significant chemical as well as a mechanical inhomogeneity is observable within the shells. This occurs on various scale levels ranging from less then one to a few houndred microns. In concert to systematic variations in micro- and nanohardness the µRS and CL analyses reveal a systematic distribution and incorporation of organic material within the shells, which is negligible within the nanocrystalline primary layer but is present in a significant amount in the innermost part of the secondary layer, next to the organic tissue of the animal. Mechanical performance (hardness and fracture toughness) of this biomaterial is mainly determined by textural features, an extreme variation of crystallite size and a purpose oriented interlikage of organic and inorganic components.