Oldest Known Rocks On Earth Discovered: 4.28 Billion Years Old

The discovery of rocks as old as 4.28 billion years pushes back age of most ancient remnant of Earth's crust by 300 million years.
The ancient rocks were found in Northern Quebec, along the Hudson's Bay coast, 40 km south of Inukjuak in an area known as the Nuvvuagittuq greenstone belt.

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UPDATE:
Discovery of world's oldest rocks challenged
Geologists in Canada may have discovered the oldest rocks on Earth. But a controversy over the techniques used to date the rocks is threatening to overshadow the discovery.

Full story on NewScientist