The Minden Coalfield (German: Mindener Revier) is located in the northern Wiehen foothills near the German town of Minden. Here, seams of Wealden Coal (Wealdenkohle) reach the surface of the earth in the Schaumburg Basin (Schaumburger Mulde). During the Thirty Years' War Swedish soldiers first discovered this black coal near Minden whilst preparing fieldworks on the Bölhorst. By 1663 it was forbidden to dig privately for coal and severe penalties were imposed for doing so.