Geologists recently dated the age of Watersmeet gneiss, a type of rock in the Upper Peninsula, as the oldest in the U.S. Here ...

Metamorphic rocks form when rocks are subjected to high temperatures or pressures. Sometimes small diamonds also form under these conditions, but so far such metamorphic diamonds have only been ...

Michigan, Minnesota and Wisconsin all feature ancient rocks known as gneisses — metamorphic rocks banded with various minerals — but an analysis determined that the gneiss in northern Michigan ...