Oldest Rock in the World

paleogeology.blogspot.com

Acasta Gneiss is dated way back to the Hadean Eon( the age of fire ) during the time when volcanism were active to form the Earth's layer. It is subjected to pressure and heat later cooling and deposited. Found in Northwest Territories, Canada, it aged 4.031 billion years and dated using the radiometric dating of zircon crystal.

Different minerals have different uranium content and zircon being used predominantly in fission tracking to determine the age of rocks.