Chuck Bednar for redOrbit.com – Your Universe Online
A rare golf-ball sized chunk of rock that contains over 30,000 diamonds could shed new light on the chemical processes that through which these metastable carbon allotropes form.
The rock, which was discovered in a diamond mine in northern Siberia, is believed to be one of just a few hundred recovered in which the diamond were still in their original setting from within the Earth, the researchers explained in a statement Monday.
After receiving the rock on load from the diamond company of Russia, ALROSA, University of Tennessee professor Larry Taylor and colleagues from the Russian Academy of Sciences studied it using a giant X-ray machine hoping to uncover clues about the gem’s origins.
Rachel Feltman of the Washington Post calls the rock “a geological rarity,” and while diamond can be worth thousands of dollars or more, each of the diamonds on the chunk of rock are less than a millimeter in size. This means that these particular diamonds only have value as a research subject, and the rock also contains speckles of red and green garnet and other minerals.
According to the researchers, scientists believe that diamonds form at depths of approximately 100 miles deep in the Earth’s mantle, and are then carried to the surface by special volcanic eruptions. However, most mantle rocks wind up crumbling during this process.
“It is a wonder why this rock has more than 30,000 perfect teeny tiny octahedral diamonds–all 10 to 700 micron in size and none larger,” Taylor explained. “Diamonds never nucleate so homogeneously as this. Normally, they do so in only a few selective places and grow larger. It’s like they didn’t have time to coalesce into larger crystals.”
He and his colleagues used the giant X-ray machine to analyze both the diamonds and their relationships with the other materials contained in the rock. In addition, they beamed electrons at the inclusions within the diamond to study the chemicals that were trapped inside.
They created both two-dimensional and three-dimensional images that revealed a relationship between different minerals. The presence of nitrogen within the diamond indicate that they were formed at higher-than-normal temperatures over longer-than-usual periods of time.
Furthermore, the images revealed the presence of carbon isotopes that are abnormal for this type of rock, indicating that it originally formed within the Earth’s crust. It was then withdrawn as the result of tectonic shifts, the study authors added, ultimately becoming the shiny rock it is today.
“These are all new and exciting results, demonstrating evidences for the birth mechanism of diamonds in this rock and diamonds in general,” said Taylor, who presented his team’s findings at the American Geophysical Union’s annual conference last December. A paper on the study is also scheduled for publication in the journal Russian Geology and Geophysics.
Research published last December revealed that diamonds can provide information about how carbon-bearing fluids move – a discovery that could provide information about how life on Earth began and what it might have looked like in its earliest stages.
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