Theoretical estimates of the ideal fracture toughness and surface energies of 48 minerals have been modelled by treating them as ionic solids, using the Born model of bonding. Development of the toughness model required calculation of the crystal binding enthalpy from thermodynamic data and the use of published elastic constants for single crystals. The principal minerals studied were oxides, sulphides and silicates, plus a few halides and sulphates, The study showed grain boundary fracture is most likely in single-phase polycrystalline minerals. However. the fracture toughness for grain boundary cracking in pure minerals is not significantly lower than that for intragranular cracking. The computed critical stress intensity values for intragranular cracking, K-IC, ranged from 0.131 to 2.774 MPa m(1/2). The critical energy release rates for intragranular cracking, G(IC) ranged from 0,676 to 20.75 J m(-2). The results are discussed with relevance to mineral comminution, including energy considerations, particle impact efficiency. and lower limiting particle size. (C) 2002 Elsevier Science Ltd. All rights reserved.