A coprecipitated xerogel with Ti:Mg atomic ratio of similar to1.3:1 was annealed for 3 h, at constant temperature in the 500-1100 degreesC range,at 100 degreesC intervals. Rietveld refinement of the XRPD scans of the products points to the formation of karroite-like metastable structures, with cell parameters, atomic positions and site occupancies that greatly deviate from those of conventional karrooite (MgO.2TiO(2) The chosen precursor composition yields a mixture of stoichiometric geikielite (MgO.TiO2) and nonstoichiometric karroite with Ti:Mg ratio (2 - x): 1; the x value calculated from the Mg and Ti occupancies found by the Rietveld refinement was 0.2 for thermal annealingat 600 degreesC and reduced nearly to zero for annealing above 1000 degreesC; the amount of geikielite increased as the annealing temperature increased. Excellent agreement was found between X-ray quantitative and structural analyses, Line broadening analysis shows considerable decrease of the microstrain as well as increase of crystallite size associated with the rise of the annealing temperature.