Abstract Amorphous fibers of a 46.5 wt% CaO-53.5 wt% Al 2O 3 eutectic compound were produced by inviscid melt-spinning. Fibers were subsequently heat treated at 900, 1000 and 1100°C for times ranging from 6 to 6000 s to elucidate crystallization processes. Fiber samples were ground for X-ray analysis. Equilibrium compounds Ca 12Al 14O 33, Ca 3Al 10O 18 and CaAl 4O 7 were present in varying amounts in all crystallized fibers. Liquid formation in fibers exposed to 1100°C for 6000 s was noted.