Cassiterite, Quartz and Sericite (Muscovite variety ).
Location: Panasqueira Mine, Covilhã, Castelo Branco, Portugal.
Sample with 2.7 x 2.1 x 1.8cm. Cassiterite in subeuhedral crystals, dark brown and opaque with adamantine lustre on a matrix of prismatic Quartz and subeuhedral crystals of Sericite (white to light brown/beige). 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.