Minerais do grupo da crichtonita em veios de quartzo da Serra do Espinha?§o (Minas Gerais e Bahia)

摘要

Four minerals of the crichtonite group found in hydrothermal quartz veins that cross several units of the Espinha?§o??Supergroup in the Espinha?§o Mountain Range are described in this paper. These minerals, senaite, crichtonite, almeidaite and??gramaccioliite-(Y), were collected in two regions Presidente Kubitschek, south from Diamantina (State of Minas Gerais),??and Novo Horizonte, in the Western Diamantina Tableland (State of Bahia). The age of these veins are related with the end??of Brasiliano Cycle, at ca. 490 Ma. Senaite is a mineral discovered in Brazil and is usually recognized in diamonda??bearing??alluvial deposits of the Diamantina region. Its occurrence as a primary mineral in situ is for the first time described here.??Although crichtonite has been known for quite a long time, its first occurrence in Brazil has been reported in the same region??in Minas Gerais. Almeidaite is the 61th a??newest Brazilian minerala?? and has been found in the region of Novo Horizonte.??Gramaccioliite-(Y), a species discovered in the last decade in Italy, has also been described for the first time in Novo??Horizonte, Bahia. The deposits and the chemical compositions of these rare minerals are characterized in this paper, as well??as the problems involved until their final recognition.