a mineral of the complex oxide class; an intermediate member of the isomorphous series of solid solutions of magnetite (FeFe2O4), ulvospinel (Fe2TiO4), and magnesian ulvospinel (Mg2TiO4). Titanomagnetite is also the name for magnetite with inclusions of the decay products of solid solutions (ulvospinel, ilmenite) and of the substituents of the decay products (rutile, brookite, perovskite).
In nature, there is an extremely wide distribution of magnetites having a high content (up to 37 percent) of the ilmenite component that retain their cubic structure despite vacancies in the tetrahedral and octahedral sublattices. These magnetites are referred to as titanomaghemites. The crystal structure is of the inverted spinel type. The parameter of the unit cell increases in the magnetite-ulvospinel series from 8.39 to 8.53 angstroms. Titanomagnetite contains admixtures of Al3+, V4+, Gr3+, and Mn2+. It occurs as octahedral crystals and, more frequently, granular aggregates and black masses. Hardness on Mohs’ scale is 5.0–5.5, and the density is 4,800–5,300 kg/m3. Titanomagnetites are decidedly ferrimagnetic, although ulvospinel is strictly paramagnetic. The two ranges of Curie points characteristic of titanomagnetite are 0°–100°C (for ulvospinel with an FeFe2O4 content up to 20 percent) and 500°–570°C (for magnetite with an Fe2TiO4 content up to 10 percent). Partial decomposition of the solid solution gives rise to autoreversal of thermoremanent magnetization in titanomagnetite, a phenomenon used in paleomagnetic studies.
Titanomagnetite deposits (basically magmatic) occur in association with ultrabasic, basic, and alkalic rocks; they also occur in placers. Titanomagnetite is used in producing iron, titanium, and vanadium.
G. P. KUDRIAVTSEVA