The oldest rock on earth

The earth is believed to be 4.6 billion years old, but how far back can this history be traced from rocks found on earth? The quest by geochemists worldwide is beginning to uncover the existence of a number of extremely old rocks dating back around 4 billion years or more located at the center of various continents. The exhibit on display here is the "Acasta gneiss" found in Canada. Radioactive dating indicates that this rock was formed 3.962 billion years ago.
The oldest mineral is one found in western Australia, and is estimated to be around 4.4 billion years old.