Researchers have confirmed crystals discovered over 15 years ago, dating back at least 4.374 billion years, are the oldest rock fragments ever found on Earth, according to a new study.

The ancient zircon crystals were discovered in Western Australia.

Research was reported in the journal Nature Geoscience.

"We've proved that the chemical record inside these zircons is trustworthy," said John Valley, lead study author and a geochemist at the University of Wisconsin, Madison, according to LiveScience.com.

Trace elements in the oldest zircons discovered in Australia's Jack Hills suggests they came from "water-rich," granite-like rocks such as granodiorite or tonalite, according to studies.

What the research means is Earth began forming a crust a lot earlier than most experts believed, following the giant impact that created the Earth-Moon system some 4.5 billion years ago.

"That age is 300 million years older than the oldest previously dated age (of other rocks,) and only 100 million years after the magma ocean," said Valley.

Zircons are considered one of the toughest minerals on the planet.

Ancient Australian crystals date back to around 165 million years after Earth formed.

Valley and his co-workers used uranium-lead radioactive dating to determine the age of the zircon crystal sample, according to the study.

Professor Samuel Bowring of the Massachusetts Institute of Technology wrote a piece on the research that he feels the findings essentially shows Earth's water didn't need to come from asteroids.

Instead, water was already present in the liquid magma ocean, which created the zircon crystals.

"We'll never know how much water there really was, but the simplest interpretation of those zircons coming from granitic rocks, is that we had a hydrous planet right from the very beginning," said Bowring. "The water was probably accreted with the rest of the parts of the Earth as the planet formed."

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