Non-caking mine rock dust for use in underground coal mines

A method for using a composition for use as rock dust in an underground mine is disclosed. The composition includes a fine, wet ground inorganic particulate material treated with at least one hydrophobic treatment, and a coarse, untreated, dry ground inorganic particulate material. Also disclosed is a composition including coal dust and mine rock dust including a fine, wet ground inorganic particulate material treated with at least one hydrophobic treatment, and a coarse, untreated, dry ground inorganic particulate material. The amount of mine rock dust may be sufficient to render the coal dust explosively inert according to at least one of a 20-L explosibility test or an ASTM E1515 explosibility test. The fine, wet ground inorganic particulate material may be calcium carbonate. The coarse, untreated inorganic particulate material may be calcium carbonate. The fatty acid may be stearic acid.