Location: Panasqueira Mine, Covilhã, Castelo Branco, Portugal.
Cluster of striated prisms of Arsenopyrite on a matrix of cream colored rhombohedral Siderite. Sample with 6.3 x 6.0 x 2.8cm and 155 grams. 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.