Joppenbergh Mountain is a nearly 500-foot (152 m) mountain in Rosendale Village, a hamlet in the town of Rosendale, in Ulster County, New York. The mountain is composed of a carbonate bedrock overlain by glacially deposited material. It was named after Rosendale's founder, Jacob Rutsen, and mined throughout the late 19th century for dolomite that was used in the manufacture of natural cement. Extensive mining caused a large cave-in on December 19, 1899, that destroyed equipment and collapsed shafts within Joppenbergh. Though it was feared that several workers had been killed, the collapse happened while all the miners were outside, eating lunch. Since the collapse, the mountain has experienced shaking and periodic rockfalls.