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Bajoca Mine, Almendra, Vila Nova de Foz Côa, Guarda District, Portugal

Mina da Bajoca, Almendra, Vila Nova de Foz Côa, Distrito da Guarda, Portugal

Largest feldspar mine in Portugal 4 Km to the W of Almendra. 700 meters long and up to 35 meters in width.

The Bajoca mine pegmatite vein is the main body of an open pit exploitation, linked to the Ceramic Industry, although Bajoca mine was a tin mine in the last century. This vein has an extension of 700 meters, with variable thickness between few meters and more than 30 meters. It is clearly intrusive in the metasediments of the “Complexo Xisto-Grauváquico”, showing a general orientation N10º with dip variations between 30º and 45º W.
During the research work done in the main vein of the Bajoca mine, was clearly showed the existence of lithium minerals, that occurs as montebrasite-ambligonite and mainly as petalite. The montebrasite-ambligonite appears as accessory mineral, in milimetric crystals. The petalite occurs as microcristaline mineral masses, white in color, or in centimetric crystals with perfect cleavage {001}. Is an essential mineral in the vein hanging wall area, what means that it is considered zoned in terms of lithium, because the foot-wall is almost sterile, with a significant enrichment to the roof zone.
These rare element pegmatites are considered by Cerny classification as LCT (Li, Cs,Ta) family. They are of the complex type, as lepidolite subtype meanwhile the main vein of Bajoca mine is classified as petalite subtype.
The worldwide growing needs of these raw materials, could and should be a motivation to the development of a new industry in this region. As we know this region (NE of Portugal) as several problems related to industrial and human desertification. This new industry as special characteristics, showing a smaller environemental impact compared to the anciente exploitations of tin and other ore minerals. They have small dimension in time and space, making this possible with small mining coumpounds, and plants more friendly to the environment.
Abstract: Carlos Miguel Pedroso de Almeida, Estudo do Filão Aplitopegmatítico da Mina da Bajoca, Almendra. Contribuiçao Científico-Tecnológica. Departamento de Geologia, Faculdade de Ciências da Universidade do Porto, Porto, 2003.

Mineral List

Albite
'Apatite'
Cassiterite
'K Feldspar'
'Limonite'
Montebrasite
Muscovite
Petalite
Quartz


9 entries listed. 6 valid minerals.

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References

Romeu Vieira, Alexandre Lima (2007) Locality No. 2, Bajoca Mine, Almendra, Portugal, in Alexandre Lima & Encarnación Roda Robles ed. (2007) Granitic Pegmatites: the state of the art - Field trip guidebook. MEMÓRIAS No. 9, Univ. do Porto, Faculdade de Ciências, Departamento de Geologia pp 49-54.

VI Congressso Nacional de Geologia, Monte de Caparica, 4 a 6 de Junho de 2003: [resumos das comunicações] / Departamento de Ciências da Terra [et al.]; apresentação Miguel Telles Antunes - Monte de Caparica: Universidade Nova de Lisboa. Faculdade de Ciências e Tecnologia, 2003. - p. 75.

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