Kohinoor secret deep inside Earth

New York: The world’s biggest and most-valuable diamonds like the famed Kohinoor may have formed from metallic liquid deep inside the Earth’s mantle, according to a new study.

Researchers from the Gemological Institute of America studied the unique properties of diamonds with similar characteristics to famous stones such as the Cullinan, Constellation and Kohinoor by examining their so-called “offcuts,” which are the pieces left over after the gem’s facets are cut for maximum sparkle.

They determined that these diamonds sometimes have tiny metallic grains trapped inside them that are made up of a mixture of metallic iron and nickel, along with carbon, sulphur, methane and hydrogen.

These inclusions indicate that the diamonds formed, like all diamonds, in the Earth’s mantle, but they did so under conditions in which they were saturated by liquid metal.

As unlikely as it sounds, their research shows that pure carbon crystallised from this pool of liquid metal in order to form the large gem diamonds.

“The existence of this metal mixture has broad implications for our understanding of deep Earth processes,” said Evan Smith from the Gemological Institute of America.

Diamonds form deep in the Earth’s mantle and shoot to the surface in minor volcanic eruptions of magma.

Impurities contained inside diamonds can teach geologists about deep Earth chemistry under the pressure, temperature, and chemical conditions in which they were formed.