The release of tritium from single crystalline quartz and from fused silica has been measured following 40 keV ion bombardment to a dose of 4 × 1011 ions/cm2. The release can be explained by normal volume diffusion with D0=101±1 cm2 sec-1 for both materials and activation enthalpies of (42 ± 5) kcal/mole for quartz and (52 ± 5) kcal/mole for fused silica. Release from quartz is faster than release from fused silica. This latter diffusion process, however, is essentially slower than diffusion of hydrogen during permeation. Possible reasons for this discrepancy are the existence of radiation damage due to the ion bombardment or the chemical state of hydrogen which cause a different elementary process for mass transport: Hydrogen diffuses in molecular form during permeation whereas probably tritium atoms or ions will diffuse following ion bombardment.