Dating rocks by trails of destruction main content.

Dating rocks by trails of destruction

Part of Hall of Planet Earth.

Pakistan gneiss

Exhibition Text

This 1.85-billion-year-old gneiss and the one-million-year-old granite vein cutting through it were dated by counting the number of fission tracks in the apatite (calcium phosphate) crystals contained in each rock. Fission tracks are microscopic scars left behind when t