New York, Jan 6 (IANS): A professor from the University of Tennessee in the US is studying a rare rock covered with as many as 30,000 diamonds. The diamonds may hold clues to the gem's origins.

The golf ball sized chunk of rock contains diamonds, each less than a millimetre in size (rendering them worthless), along with speckles of red and green garnet and other minerals.

The rock was found in Russia's Udachnaya diamond mine in northern Siberia.

"It is a wonder why this rock has more than 30,000 perfect, tiny octahedral diamonds - all 10 to 700 micron in size and none larger," said earth and planetary sciences professor Larry Taylor.

Taylor and his colleagues are examining the sparkly chunk using a giant X-ray machine.

They also beamed electrons at the materials inside the diamonds to study the chemicals trapped inside.

This created two and three dimensional images which revealed abnormal carbon isotopes for this type of rock, indicating it was originally formed as part of the crust of the Earth, withdrawn by tectonic shifts and transformed into the shimmery rock we see today.

Scientists believe that diamonds form some 100 miles deep in the Earth's mantle and are carried to the surface by special volcanic eruptions.

However, most mantle rocks crumble during this journey.

This rock is one of only a few hundred recovered in which the diamonds are still in their original setting from within the Earth, Taylor said.

The findings were presented at the American Geophysical Union's annual conference in San Francisco in December and will be a part of the forthcoming special issue of Russian Geology and Geophysics this month.