  Monte Carlo simulations were used to study the assembly of binary mixtures of
hard disks with squares, where the components have size ratios that optimize
their co-assembly into compositionally disordered solids. It is observed that,
along with the enhanced regions of solid miscibility, a continuous-looking
transition from the disk-like to the square-like behavior occurred through a
novel mosaic (M) phase, which seamlessly bridges the regions of hexatic
mesophase of disks and the tetratic mesophase of squares. The M phase has
interspersed tetratic, hexatic, and rhombic-like locally ordered clusters.
