We examine the structures and orientation of charged colloidal silica crystals formed by the unidirectional diffusion of sodium hydrogencarbonate. Angular-dependent diffraction spectrometry is applied to centimeter-sized cubic crystals immobilized in polymer hydrogels. We find that the lattice planes of these crystals are not aligned with the container walls. This suggests that these large crystals are not formed by the wall effect, which has played a vital role in the formation of large crystals in previous studies.