The kinetics of partial melting in a P-spodumene glass-ceramic was measured by holding fully crystallized material above the solidus but below the liquidus temperature. The kinetics was apparently limited by the rate of diffusion of silica in the crystalline phase. The measured lattice diffusivity of silica was 8 X 10-lo exp(-251 kJ mol-l/RT) m2 s-l with a possible error of f 6 0 kJ mol-l in the activation energy. The partially molten samples were heat-treated below the solidus to obtain the kinetics of crystallization, which was found to be interface-reaction-controlled.

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