Cassiterite, Quartz, Sericite (Muscovite variety ) and Tourmaline .
Location: Panasqueira Mine, Covilhã, Castelo Branco, Portugal.
Sample with 3.3 x 2.5 x 2.2cm. Euhedral to subhedral crystals of Cassiterite, dark brown and opaque with an adamantine lustre on a matrix of prismatic subhedral crystals of Quartz, Sericite (white to light brown/beige) and small transparent needles of Tourmaline. 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.