Serrabrancaite, MnPO4 center dot H2O, a new mineral from the Alto Serra Branca pegmatite, Pedra Lavrada, Paraiba, Brazil

Serrabrancaite is a new manganese phosphate from the Alto Serra Branca pegm atite near Pedra Lavrada, Paraiba, Brazil. The mineral occurs as dark brown to dark greenish black isometric crystals up to 0.3 mm size. The crystals have an adamantine luster and are translucent. Chemical analysis yields (in wt%) Mn2O3 = 46.85, P2O5 = 42.72, H2O = 9.8, total = 99.37. The empirical formula is Mn0.98P1.00O3.98. 0.90 H2O, simplified to MnPO4. H2O. Serrabranc aite is monoclinic, space group C2/c, with unit-cell parameters a = 6.914(2 ), b = 7.468(2), c = 7.364(2) Angstrom, beta = 112.29(3)degrees, V= 351.8(1 ) Angstrom(3). The measured density is 3.17(1) g/cm(3), the calculated dens ity for Z = 4 is 3.16 g/cm(3). Serrabrancaite is isostructural with the sul fates of the kieserite group. The mineral is an alteration product from a p hosphate pegmatite and is accompanied by vernadite and phosphosiderite.