The tiny diamonds were found trapped in zircon, a rare and exceptionally stable mineral that forms under temperatures between 1,112 and 1,652 Fahrenheit (600 and 900 degrees Celsius).
Once zircon has crystallized it may be moved around by geological processes, but its chemical makeup and structure don't change. This makes its age easy to pinpoint.
Zircon crystals represent the only record of the first 400 million to 500 million years of Earth's history, Wilde explained.
By analyzing a crystal's trace minerals and structure, geologists can deduce the conditions under which it formed.
About 4.5 billion years ago, Earth developed from a cloud of dust around a proto-sun. During its youth, Earth smashed into a planet-size body and its surface temperatures likely soared above 10,830 degrees Fahrenheit (6,000 degrees Celsius). When the molten Earth cooled, the liquid lava gelled into rocks. Details about the rocks and when they began to form, a subject of intense debate, have been limited by sparse data.
One such debate centers on whether early Earth was covered by oceans of hot lava or if the planet's surface had cooled enough for rock formation and was covered instead by oceans of water.
The scientists, led by Martina Menneken of the Institute of Mineralogy, ran chemical analyses of the zircons, finding the ancient crystals (and thus the enclosed diamonds) were more than 4 billion years old. That's nearly a billion years older than the previous oldest-known terrestrial diamonds and suggests the diamonds were present in material that crystallized within 300 million years of the formation of Earth, the scientists say.
Diamonds are made out of carbon-highly organized carbon, that is. Geologists are still guessing how diamonds formed in the Earth from 1 billion to 3 billion years ago, according to a recent study in the journal Nature, but they think the recipe follows something like this:
Bury carbon dioxide 100 miles into Earth.
Heat to about 2,200 degrees Fahrenheit.
Squeeze under pressure of 725,000 pounds per square inch.
Quickly rush towards Earth's surface to cool.
By Mayline C. Homecillo
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