Watersmeet gneiss is found in Michigan's Upper Peninsula. Minnesota's Morton gneiss previously held the title for oldest rock in the U.S. Scientists recently unveiled the nation's newest "oldest ...

In a geologic nutshell: Two ancient types of rock - 1.4-billion-year-old Oracle granite and 50-million-year-old wilderness granite combined to form a type of rock called gneiss. A display in the ...