Scientists have discovered what they believe are the world's oldest diamonds, dating back more than four billion years. The scientists, from Australia and Germany, unearthed the diamonds in the outback of Western Australia. VOA's Jessica Berman reports the scientists say the diamonds may revise theories about Earth's formation.

At 4.2 billion years old, the diamonds are thought to be as old as Earth itself.

No more than a hair thin, the precious specks were found embedded in ancient zircon rocks by geologists analyzing samples taken from the Jack Hills region of Western Australia.

Geologist Martina Menneken, who led the team of German and Australian researchers that discovered the diamonds, says everyone was really surprised.

"We were really going crazy because [of] the implications and what this means [about the] conditions of early Earth are really amazing," said Martina Menneken.

The scientists say the diamond specks may shed light on the period of the earth's creation from a giant cosmic dust cloud to a planet.

The time between the creation of the Earth around 4.5 billion years ago and the formation of the oldest-known rocks some 500 million years later is known as the Hadean period - the "dark ages" of geology.

In the past, geologists have thought of it as a time when the surface of the planet was a mass of molten lava. But the discovery of the ancient diamonds challenges that view.

Menneken said the presence of diamonds implied there was a relatively thick continental crust as early as four 4.25 billion years ago.

This suggests it may have taken only around 200 million years for the Earth's surface to cool enough for the formation of rocks.

Researcher Thorsten Geisler explains diamonds are formed under extremely high pressure, and investigators think the tiny diamond flecks could only have been produced by pressure exerted on a cooler, solid Earth surface.

"To reach these conditions, we need a thick continental crust," said Thorsten Geisler. "And so far, people thought we had no continental crust as early as 4.25 billion years [ago]. And this is the big impact I think we have - that we needed to have these conditions to form diamonds."

Martina Menneken says the notion of a cooler Earth millions of years earlier than previously thought raises some interesting possibilities.

"If it already has been that cool, maybe we do have an ocean already," she said. "And when we think about an ocean, we think about water on Earth that early. And I think the next thought might be if we have an ocean, maybe it was really early life."

News of the ancient diamond discovery is published in the journal Nature.