The Highlands Physiographic Province is a geological formation composed primarily of Precambrian igneous and metamorphic rock running from the Delaware River near Musconetcong Mountain, northeast through the Skylands Region of New Jersey along the Bearfort Ridge and the Ramapo Mountains. Numerous abandoned mines dot the region, dating from the 18th and 19th centuries when iron, copper, zinc and other minerals were extracted from the formations. The glaciated northern half of the province has an abundance of lakes and reservoirs which serve as water supplies for the urban areas to the east. The region's watershed is protected by the Highlands Water Protection and Planning Act.