Scientists say the zircon crystal has been accurately determined to be 4.374 billion years old by two independent methods.
Writing in the journal Nature Geoscience, lead author John Valley of the University of Wisconsin says the crystal is 300 million years older than any other ancient rocks previously found.
He said the zircon stone was formed only about 100 million years after the world was covered by a magma ocean, and came from the time when the Earth started making a crust.
The age of the crystal was determined by using uranium-lead radioactive dating as well as atom-probe tomagraphy after it was found in sandstone about 500 miles north of Perth.
The period of Earth’s history when the zircon crystalized is known as the Hadean eon, named after the ancient Greek god of the underworld, Hades.
The name is appropriate because of the hellish conditions that prevailed as Earth was forming.
There is evidence of water when the crystal took shape, leading scientists to believe that the liquid was present long before asteroids and comets brought more of it when they bombarded the planet about 4 billion years ago.
Photo: John Valley - University of Wisconsin in Madison