|Tonalitic gneiss||NMNH 116542-1||Canada, Northwest Territories|
Gift of Dr. Samuel A. Bowring.
- Acasta Gneiss
- Tonalitic gneiss
- Northwest Territories, Canada
- USNM 116542
- Gift of S. Bowring, Washington University
At 3.96 billion years old, this gneiss is one of the oldest known Earth rocks. The Earth is 500 million years older still, but little record of that early time has survived our planet's geologic activity.