This pyromorphite is from the Chester County Mine in the Phoenixville mining district, Schuykill Township, Chester County, Pennsylvania, USA. This area has been mined since the middle nineteenth century for lead and copper. This mine contained eight different minerals including pyromorphite. It is a lead phosphate that contains the elements Pb, P, O, and Cl. This piece consists of an altered clay and oxide matrix that is topped on the display side with dozens of pyromorphite crystals. This piece measures 1 1/2 x 1 1/2 x 1 inches or 38 x 38 x 25 mm.