Hydrated phosphate containing hydroxyl
Specific gravity: 1.805
Solubility: Soluble in 1:10 acids (Dana)
Moraesite is a rare late-stage hydrothermal mineral in complex zoned granite
pegmatites. Associated minerals include beryl,
apatite and muscovite
The type locality is the Sapucaia mine, Sapucaia do Norte, Galiléia, Minas Gerais, Brazil. Phosphate minerals are most abundant in the central part of the granite pegmatite here; they are associated with quartz, beryl, feldspar variety perthite and muscovite. Large masses of triphylite and heterosite up to several tons in weight are the principal phosphate minerals. In addition to moraesite, other phosphate minerals include frondelite, faheyite, hureaulite, childrenite, apatite, roscherite, vivianite and variscite. Moraesite occurs on the walls of vugs that have developed in or adjacent to beryl, and on surfaces of albite, quartz and muscovite. Growths of moraesite frequently occur on the surfaces of frondelite and contain unaltered fragments of beryl (AM 38.1126-1133).
At the Humaita pegmatite, Itinga, Minas Gerais, Brazil, moraesite occurs in the oxidation zone with beryl, albite, quartz, muscovite and frondelite (Dana).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, moraesite is associated with hydroxylherderite, beryl and fluorapatite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.512).
At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, moraesite is uncommon, but when found, it generally occurs in minute crystalline voids of quartz and siderite (R&M 90.5.419).
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