Experimental data that allow the determination of an inherent fracture mode of the refractory fcc metal iridium at room temperature are considered in this paper. High purity iridium and Ir-3 wt%Re-2 wt%Ru are chosen as the model substances. Brittle transgranular fracture is the sole fracture mode exhibited by the samples at room temperature. Neither recrystallization in 10(-5) Torr vacuum nor the geometry of applied stress or grain size induce the brittle intercrystalline fracture in these materials. (c) 2005 Springer Science+ Business Media, Inc.