The handling, transport and delivery of particulate materials, particularly fine particles, may be difficult. Alkaline earth metal oxide particles such as magnesium oxide (MgO) may be suspended in glycerin and/or alkylene glycols such as propylene glycol up to loadings of 51 wt%. Such suspensions or slurries make it easier to deliver MgO and similar agents into fluids, such as aqueous fluids gelled with viscoelastic surfactants (VES). These concentrated suspensions or slurries may be improved in their stability by the inclusion of minor amounts of a vegetable oil and/or a fish oil The MgO serves as stabilizers and/or fluid loss control agents for VES-gelled fluid used to treat subterranean formations, e.g. for well completion or stimulation in hydrocarbon recovery operations. The particle size of the magnesium oxide or other agent may be between 1 nanometer to 0.4 millimeter.