A good synthetic or well-characterized natural ilmenite standard would be nice to have. First, it’s a common mineral that needs to be analyzed accurately, especially when trying to ascertain Fe2O3 content. Second, when I use rutile and hematite as respective Ti and Fe standards, I often get greater than one Ti atom per three-oxygen formula unit. Overestimation of TiO2 content and underestimation of FeO has been noted by others when using rutile and hematite as standards (see attached paper by Evans et al., p. 152 and appendix). The errors tend to offset and produce an oxide total near 100% and result in underestimation of Fe2O3 (from charge balance). Last, the only ilmenite standard available from the Smithsonian is USNM 96189, which is visibly inhomogeneous (see image below) and has an analysis total of only 99.4%. When I do wavelength scans, I don’t see anything other than Ti, Fe, Mn, Mg, and Nb, which are all accounted for in the wet chemical analysis.
Does anyone know if it is relatively easy to synthesize ~100-micron ilmenite crystals, for instance by a reaction such as Fe + Fe2O3 + 3TiO2 = 3FeTiO3 in an evacuated silica glass tube?
Ilmenite USNM 96189: