We have found the finite elasticity and characteristic visco‐elastic relaxation in novel mosaic phases of the non‐symmetric chiral twin liquid crystal. X‐ray scattering experiment shows the mosaic phase possesses smectic layer structure, but its intensity rather weak in comparison with smectic phase, and appears in the higher temperature and optical purity region than TGB phase. Thus, defects of the smectic layers are three dimensionally dispersed in the mosaic phase, and interacted with each other by the spatial deformation of the layers. Correlation of defects produces the macroscopic mobility and the unique visco‐elastic properties. These relaxation phenomena can be expected to relate to the intrinsic feature of the collective hydrodynamic modes in the defect lattices systems. © 2004 American Institute of Physics