A particulate composition for use in alumina-magnesia spinel forming dry vibratable mixtures may include, based on the total weight of the particulate composition, from 95 to 99.9 wt % of a mixture of particulate Al2O3 and particulate MgO, and from 0.1 to 5 wt % binding agent, wherein at least a portion of the particles of said mixture of particulate Al2O3 and particulate MgO is present in the particulate composition as a coating of particles on the surface of other particles. Methods of producing and using the particulate composition are also described.