An outcropping of Greenstone rock is located in Ely. Greenstone is one of the olest known Minnesota rocks and it is located just a few blocks off Camp Street in Ely, Minnesota.It is called Pillow Rock because of the clearly visible rounded shapes formed within this mass of lava flow. An effort has been underway to remove Pillow Rock to a location more accessible to tourists.
An excellent example of an ellipsoidal lava flow said to be 2.7 billion years old with peculiar masses formed when dark lavas flowed under water. One of the few specimens of its kind in the world. The rock is an outcrop of Ely Greenstone.