The Silurian Shawangunk Formation is a mapped bedrock unit in eastern Pennsylvania, New Jersey, and New York.

The Shawangunk is defined as a light to dark-gray, fine to very coarse grained sandstone and conglomerate, containing a few shale interbeds.

[4] Very few fossils exist in the Shawangunk; however, Eurypterids can be found in the middle portions of the formation roughly 420–750 feet from the base in some locations in New York State.

Relative age dating of the Shawangunk places it in the Lower Silurian period, being deposited between 440 and 417 (±10) million years ago.

[6] The hardness of the quartzite and conglomerate layers make the Shawangunk an excellent building stone.