Three types of mineralisation are present in the phosphate ore mined by Serrana in Araxa, Brazil: oxidised, micaceous and silicate-carbonate. The micaceous and silicate-carbonate are considered problem ores. This investigation deals with characterisation and fundamental studies performed on fractions resulting from the purification of five samples from the silicate-carbonate type collected in the mine, representing portions with visually different aspects, designated as: barite, carbonatite, green micaceous, brown-green micaceous and brown clay. Each type was purified in the laboratory and then submitted to mineralogical characterisation, zeta potential determinations, and microflotation experiments with anionic and cationic collectors. The samples, with the exception of the barite, are mineralogically complex and the selectivity between apatite and the gangue minerals is poor. The only feasible route for processing the silicate-carbonate ore is blending it with the standard oxidised ore.