[en] Evaluations of the energy for thermonuclear ignition of a compressed deuterium-tritium mixture contaminated by a high-Z material are presented. Mixing at the atomic level is considered and the results are given as a function of the contaminant fraction. The reference situation is that of cone-focused fast ignition (CFFI). The numerical 2D simulations for this study were performed by a Lagrangian 2D hydrocode that includes real matter EoS, real matter opacity coefficients, and packages for finite-range energy deposition by reaction products and the relative in-flight reactions. A simple estimate is presented for the effects of high-Z material blobs on the ignition energy (macroscopic mixing). Possible sources for fuel contamination in CFFI are discussed