Cumberlandite from Iron Mine Hill, east of Woonsocket, Rhode Island; photo by James St. John on Flickr (use permitted with attribution).
Official State Rock of Rhode Island
Rhode Island designated cumberlandite as the official state rock in 1966; a very rare variety of igneous rock. All State Rocks
Cumberlandite is magnetic and is estimated to be between 1 and 1.5 billion years old. A heavy black or dark brown rock with white markings, cumberlandite is found south of the town of Cumberland on both sides of Narragansett Bay in Rhode Island.