Summary: Samples of magnetite containing exsolution bodies of ilmenite, or of ulvöspinel and ilmenite, were heated at 1,250–1,300° C. under oxidizing and under reducing conditions.

In the former case, the product consisted of magnetite, ferri-ilmenite, and pseudobrookite. In the latter, loss of oxygen converted a magnetite-ilmenite intergrowth into a homogeneous Fe₃O₄-Fe₂TiO₄ spinel solid solution, while a magnetite sample originally carrying ulvöspinel in addition to ilmenite yielded a spinel phase with surprisingly low cell dimension, together with some metallic iron.