Block size distributions were determined for several Franciscan melanges contained within regions with measured areas (A) ranging between cm2 and km2. The data were plotted as log-histograms and were found to be individually fractal and, when normalized, collectively scale-independent. Hence, blocks will be encountered in melanges at all scales. A block/matrix threshold size for a Franciscan melange rock mass of any scale is defined as 0.05√a. A tentative generic fractal dimension of 1.3 for Franciscan melanges allows rough estimates to be made of the block size distributions of Franciscan melange rock masses, given A and the volumetric proportion of blocks.