Bundenbach is known internationally for its slate mining and important fossil finds. The use of slate in the Bundenbach area has a demonstrably long history: the Celtic hill castle’s defensive wall was built of slate quarrystones. The first slate mining lease agreement is witnessed on Saint Walpurga’s Day 1519: The Lords of Wiltberg leased their "“Laienkaul unden an Prorschitt uff der Bach gelegen”" (“"Laienkaul" down below at Bruschied, lying on the brook”) for four years to, among others, the two Bundenbach residents Peter and Niklas Huppen.