Cassiterite with Siderite

specimen number:
8911126

location:
Panasqueira Mines, Sao Jorge da Beira, Covilha, Castelo Branco, Portugal

description:

Lustrous slightly translucent crystal of cassiterite measuring 1.3 x 1.2 x 0.7 cm in size along one edge of a siderite and quartz crystal covered matrix. In good condition. Nice example for the species and locality. The specimen comes with a previous label from the Alton collection.

The Panasqueira Mines in Beira Baixa, Portugal, opened in 1898 and, aside from a brief temporary closure in 2003, remain actively in operation today. Geologically, the deposit is hosted within a sequence of late Precambrian to Cambrian metasedimentary rocks, primarily consisting of greenschist-facies shales, slates, and greywackes of the Beira schist formation. The mineralization occurs as a sub-horizontal system of quartz veins rich in tungsten, tin, and copper, which are genetically related to an underlying hidden Hercynian granitic pluton emplaced during the Late Carboniferous period.

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