Ulvospinel

Ulvospinel

 

a mineral of the subclass of multiple oxides, Fe2Ti04. Ulvospinel crystallizes in the isometric system, and its structure is the inverted form of the spinel structure. It forms solid solutions with magnetite. Lattice disintegration structures form upon cooling. Ulvospinel is found in the form of irregularly shaped black grains and phenocrysts. The unit cell parameter a0(8.40-8.53 Á), the Curie point (from 580° to - 150°C), and the density (5,200-4,800 kg/m3) vary in a regular manner in the magnetite-ulvospinel series. Upon oxidation, ulvospinel alters to ilmenite. It is found in ultrabasic magmatic rocks and lunar basalts. Ulvospinel is a component of complex titanium-magnetite ores.

References in periodicals archive ?
Petrographic studies on glass-bearing burned rocks reveal the occurrence solid solution series as magnetite-hercynite (Fe[Al.sub.2][O.sub.4]), ulvospinel ([Fe.sub.2]Ti[O.sub.4]), hematiteilmenite (FeTi[O.sub.3]), y magnesiumferrite along the spinel (Mg[Al.sub.2][O.sub.4])-magnesiumferrite (Mg[Fe.sub.2][O.sub.4]) join of [Sp.sub.80][Mf.sub.20] and along the magnesioferrita-hematita join of [Mf.sub.60][Hm.sub.40] (Cosca et al., 1989).
The encountered natural magnetite is represented by a solid solution of [Fe.sub.3][O.sub.4] (magnetite) and [Fe.sub.2]Ti[O.sub.4] (ulvospinel).
The contents of the magnetite component in the analysed grains are very high, 99 mol.%, with negligible amounts of the ulvospinel component (0.1-1 mol.%).
The composition of larger lobate grains shows their pertinence to titaniferous magnetite with a higher content of ulvospinel molecule ([Fe.sub.2]Ti[O.sub.4]) and low contents of Mn, Mg, Al, thus forming very low proportions of jacobsite, magnesioferrite, and hercynite, respectively, and sometimes V.
Okorusu magnetites exhibit abundant exsolutions of ulvospinel in a characteristic cloth texture, and oxidation exsolution occurred subsequently.