Acasta Gneiss

At 4 billion years old, this gneiss is the oldest known rock that formed on Earth. The Earth is about 500 million years older still, but little record of that early time has survived our planet's geologic activity.

Group: Metamorphic
Catalog Number: USNM 116542
Time Period: 4 billion years old
Gift of S. Bowring, Massachusetts Institute of Technology
Locality: Northwest Territories , Canada