Moraesite from the Humaita tourmaline mine, Minas Gerais, Brazil
La moraesite de la mine de tourmaline de Humaita, Minas Gerais, Bresil
The Canadian Mineralogist (September 1987) 25, Part 3: 419-424
Moraesite occurs as a coating in pockets of the Humaita granite pegmatite, which is worked for gem-tourmaline, near the Jequitinhonha River in the northern part of Minas Gerais, Brazil. Its powder-diffraction data, chemical composition, and refractive indices are compared with those of moraesite from the type locality, the Supucaia mine in the same state, and the latter two with moraesite from a number of other localities. Wet-chemical analysis, XRD data, thermal analyses (DTA and TGA), and its IR absorption spectrum indicate that an appropriate formula is (Be (sub 1.594) Ca (sub 0.286) Mn (sub 0.092) Fe (sub 0.028) ) (sub 3.5) (PO (sub 4) ) (sub 2) (OH) (sub 0.8) .7H (sub 2) O rather than that originally proposed by Lindberg et al.