Location: Panasqueira Mine, Covilhã, Castelo Branco, Portugal.
Aggregate of small prismatic crystals of Arsenopyrite with strong silver metallic lustre covered by small curved rhomboedric crystals, with 1-2mm, of light cream Siderite. Sample with 3.2 x 2.5 x 2.0cm. 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 graywayckes.