engleski

Mineralogy of the Boa Vista pegmatite, Galiléia, Minas Gerais, Brazil

Samples of accessory minerals were collected at the Boa Vista pegmatite, belonging to the Eastern Brazilian pegmatite province (EBP) for mineralogical studies. A total amount of 21 mineral species, half of which belongs to the phosphate mineral group were determined using optical polarizing microscopy, X-ray powder diffraction and scanning electron microscopy. Common pegmatite minerals found in this pegmatite are albite, microcline, quartz, beryl, spodumene and mica. Phosphates identified with used methods in the Boa Vista pegmatite are: hureaulite, cyrilovite, phosphosiderite, variscite, heterosite, strengite, rockbridgeite, metatorbernite, frondelite and scorodite (arsenate). The other accessory minerals are cryptomelane, löllingite, fourmarierite, bütschliite, and bismuth. This is the first systematic investigation of mineral samples from Boa Vista pegmatite. Six minerals were described for the first time in that pegmatite (fuormarierite, bütschliite, hureaulite, metatorbenite, strengite and scorodite). According to minerals determined, Boa Vista pegmatite can be considered as a phosphate-rich pegmatite. The phosphate assemblage occurs in miarolitic cavities up to 15 cm or in substitution to triphylite-lithiophilite. Almost all phosphates identified in the Boa Vista pegmatite are secondary by origin and they belong to the low-temperature hydrothermal mineral assemblage to weathering alteration. Only heterosite does not belong to this paragenesis because it is assumed as metasomatic phosphate.

mineralogy; Boa Vista pegmatite; phosphate mineral group

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