at the base of Blue Mountain are used for decorative stone, building stone, and aggregate. See also Geology of Pennsylvania Geology of New Jersey Blue Mountain (Pennsylvania) Kittatinny Mountain Shawangunk Ridge Lehigh Gap, Pennsylvania References Shawangunks Silurian System of North America Silurian geology of Pennsylvania Geologic formations of New Jersey Geologic formations of New York (state) Sandstone in the United States Silurian southern paleotemperate deposits