These arsenopyrite crystals are from the Panasqueira Mine – Couto Mineiro Panasqueira, Covilha, Castelo Branco District, Portugal. This is a large tungston and tin mine with four stages of minerallization including a sulfide stage containing arsenopyrite. It is a sulfide that contains the elements Fe, As and S. This specimen consists of clusters of complex, brass-silver colored, arsenopyrite crystals with some minor mica matrix. The crystals have a brass-silver color and sub-metallic luster. They have multiple serrated terminations and some form coxcomb formations. This piece measures 2 1/8 x 1 1/2 x 1 inches or 54 x 38 x 25 mm.