Terrestrial zircon and apatite, as examples of uranium rich refractory minerals, and chromite, also highly refractory but
uranium poor, were neutron-irradiated for their133Xe release studies. Uranium determination by133Xe was found not to be successful in these refractory samples, due to incomplete fissiogenic-xenon release at 1600°C as revealed
by stepwise heating experiment. The high temperature release peaks appeared at ≾1500°C in these terrestrial minerals studied,
but at 1000∼1200°C in reported meteoritic whitlockite and chromite.