Norfolk Southern train 60I.22, consisting of hoppers full of synthetic gypsum (a gray, powdery mineral) passes through Cassandra, Pennsylvania, on June 26, 2017. NS 9802 and 8129 are up front, and on the rear are the typical pair of SD40Es (rebuilt SD50s) – in this case, NS 6326 and 6320. Synthetic gypsum (Calcium Sulfate) is a byproduct of the coal flue gas desulphurization process (i.e., scrubbing). The train is headed to USG's wallboard plant at Strawberry Ridge PA. The synthetic gypsum is used to make wallboard.