The fracture behaviour of coal flyash compacts, in which interparticle forces are relatively weak, is investigated. Notched and unnotched specimens of coal flyash compacts were tested to failure in flexure using a test method developed in this report. The fracture toughness at failure, as calculated from linear elastic fracture mechanics (LEFM), appeared to be a constant of the material for a deep notch. Significant weakening of the powder compact occurred in the presence of a crack. Coal flyash compacts with a higher moisture content showed a degree of plasticity; this is linked to an increase in the fracture toughness of these compacts.