Cassiterite, Quartz, Sericite (Muscovite variety ) and Tourmaline .
Location: Panasqueira Mine, Covilhã, Castelo Branco, Portugal.
Sample with 3.0 x 1.7 x 1.2cm. Dark brown opaque Cassiterite tetragonal crystals, with an adamantine lustre on a matrix of prismatic Quartz with subeuhedral crystals, Sericite (white to light brown / beige) and small Tourmaline needles. Formed in mineralized veins of quartz, sulfides, wolframite, cassiterite, micas, fluorite, carbonates, among others, associated with the generation of a greisen dome by granitic intrusion in Paleozoic schists and graywackes