WASHINGTON, Sept. 5 (UPI) -- Diamonds, the hardest gems on Earth, may contain secrets about the primordial days of the world, according to a new report from an international team of scientists.
The findings may not only reveal more of the inner workings of the planet, but also could help future mineralogists uncover hitherto unknown caches of the previous gems.
"Diamonds are like little time capsules," researcher Steve Shirey, a geochemist at the Carnegie Institution of Washington, told United Press International. "I find it extremely exciting to work with diamonds, some of which are 3.3 billion years old, and discover knowledge of how the Earth worked back in a time we can never observe."
In nature, diamonds are created in the extreme heat and pressure hundreds of miles deep in the Earth. Because these gems are the hardest natural substance, they can be in the Earth's mantle for billions of years.
By analyzing grit trapped in the diamonds, scientists can peer into some of the deepest parts of Earth's history, much as looking at fossils allow paleontologists to catch a glimpse of the ancient world. "They're kind of like messengers from another time," Shirey said of diamonds.
Most diamonds are contained in cratons, masses of stone hundreds to thousands of miles wide that contain the oldest rocks on Earth, around which younger continental material clusters. The diamonds harbored inside are ripped from inside the Earth during monstrously powerful eruptions that can travel at twice the speed of sound. The eruptions spit out a kind of crystal-loaded volcanic rock known as kimberlite.
"I don't think anyone's witnessed a kimberlite eruption in historic times -- they'd probably kill everything around," Shirey said.
Shirey and colleagues from the United States, Scotland, South Africa and France looked at 4,000 diamonds from the Kaapvaal-Zimbabwe craton in southern Africa. Mining companies had donated the gems to science for the largest scale diamond chemistry study ever held. By analyzing trace element and nuclear isotope compositions of the diamonds and the specks inside them, the investigators have peeled back time for details on when and how the gems and the craton formed.
The oldest generation of diamonds they looked at is 3.3 billion years old, dating back to a time when oceans covered the Earth, Shirey said. The next stage of gems are 2.9 billion years old and come from when the craton formed from two other cratons slamming together. After that, 1.6-billion-year-old diamonds arose just when the first living cells containing nuclei started appearing.
Although the researchers note their data corroborates existing seismic information, diamond geologist Mark Hutchison at the Australian National University in Canberra predicted the information contained in the tiny gems soon will help yield new knowledge about giant events in our planet's history in places such as Russia, where less remains known.
"The more you know about how the Earth works, in particular in connection with diamonds, the more you can be informed about where to look for them," Hutchison said. "Down the line, you can never really tell what kinds of spin-offs can come from esoteric research."
The scientists describe their findings in the Sept. 6 issue of the journal Science. --
(Reported by Charles Choi, UPI Science News, in New York.)
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