A curable organopolysiloxane composition is provided, which is capable of generating a silicone rubber mother mold with improved mold release durability. The composition includes (A) 100 parts by mass of an organopolysiloxane containing at least two Si-bonded alkenyl groups within each molecule, (B) an organohydrogenpolysiloxane containing at least two Si-bonded hydrogen atoms atoms within each molecule, in sufficient quantity to provide 0.4 to 5.0 mols of Si-bonded hydrogen atoms within the component (B) for each 1 mol of Si-bonded alkenyl groups within the composition, (C) 5 to 50 parts by mass of a finely powdered silica with a specific surface area measured by nitrogen gas absorption of at least 50 m.sup.2/g, (D) 0.1 to 50 parts by mass of heavy calcium carbonate with a specific surface area measured by air permeability of 0.5 to 2.5 m.sup.2/g, the surface of which has been treated with a paraffin-based compound, and (E) an effective quantity of a platinum group metal-based catalyst.