As of February 23, 2014, where was the earth’s oldest known zircon crystals found?

Scientists examined a fragment of zircon crystal from Australia’s Jack Hills and discovered that it was the oldest ever found. The rock is 4.375 billion years old, give or take six million years. In total, three Jack Hills zircons have been tested and found to be nearly as old as the earth itself, 4.54 billion years old. The Australian crystals formed only 165 million years after the planet formed.

John W. Valley, PhD, and his team of researchers from the University of Wisconsin, Madison, published their findings in the February 23, 2014, edition of the journal, “Nature Geoscience”. They used a technique called atom-probe tomography (APT) to enhance rock-age findings based on the decay of uranium atoms.

Uranium atoms radioactively decay to lead. APT allows investigators to count the lead atoms in the zircon crystals, one by one. This method allowed the Valley team to end a controversy about the age of the Jack Hills zircons, which had been roiling for decades. The discovery leads to the conclusion that Earth was hospitable much earlier than previously established.