The structural disorder and twin microtexture of (Ba0.24Ca0.76)(2)SiO4 crystal were investigated by X-ray powder diffraction, precession method, and optical microscopy. The crystal at 298 K was orthorhombic (space group Pnma, Z=4) with a=0.70490(5) nm, b=0.55399(4) nm, c=0.95532(7) nm, and V=0.37306(4) nm(3). The crystal structure was satisfactorily described by a split-atom model, involving the positional disorder of Ba/Ca and O atoms across the (010) mirror plane. The crystal was found to be isostructural with alpha'(H)-Ca2SiO4, thus regarded as the stabilized alpha'(H) phase. The crystal grain was composed of orthorhombic domains in three different orientations. The unit cells within each domain were related to one another by the threefold pseudo-symmetry axis lost during the alpha-to-alpha'(H) transition. Each domain was most probably made up of sub-domains of the two mirror-related structural configurations with P2(1)/n symmetry.