Résumé
Two new rare-earth-bearing members of the epidote group are described from carbonate pods in Mn-rich metacherts. According to the structure refinements, Mn occurs mainly in the divalent state in both of them and occupies both the large A1 site instead of Ca and the large octahedral M3 site instead of Al or Fe 3+ , charge-compensating the substitution of Ca 2+ by REE 3+ in the largest, A2 site. The two minerals are therefore members of the androsite series. Manganiandrosite-(Ce) has dominant Mn 3+ in the M1 site; it occurs at the Praborna manganese mine, Saint-Marcel, Aosta valley, Italy, in a Mesozoic eclogite-facies ophiolitic unit of the western Alps. Associated minerals are rhodochrosite and Mn-pyroxenoid, with minor calderite, spessartine, hematite and pyrophanite. The structural formula is A1 [Mn 2+ 0.60 Ca 0.40 ] 7 = 1 [A1] Mn analogue of khristovite. Even in these Mn-rich systems, incorporation of F on O4 is balanced by Mg and not Mn incorporation. The variety of mineral assemblages in Mn-V-REE-rich systems is discussed on the basis of oxidation state.