hydroxyapatite is favored at increasing acidity (q(H2O)Na). As a general trend, a q(Sr) increase favors Sr5(MnO4)3OH at the expense of SrMnO3 (Figure -C, details in Figure ). Besides, Na0.7MnO2 appears for low Sr contents (q(Sr) = 1). No Na-containing phase analogous to KSrMnO4 is reported, so that in the low q(H2O)Na region (≤ 1.6), if the Sr content is low (q(Sr) ≤ 2), no Mn(V) phase can forms and the perovskite SrMn IV O3 is obtained. If q(Sr) increases (q(Sr) = 4), the large excess of strontium enables stabilization of the hydroxyapatite Sr5(MnO4)3OH.