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Ocean floor sediments recycle to form salty diamonds

As per the reports of a new study by a team of geoscientists from Macquarie University, Sydney, salt traces trapped in many diamonds reveal on analysis that the stones are produced from the seabeds which have been trapped inside the Earth’s crust for countless years.

A majority of the diamonds which are found on the surface of the Earth are formed in this manner while the others are formed due to the melt crystallisation quite deep in Earth’s mantle. In the experiments, researchers from Goethe Universität and Johannes Gutenberg Universität of Germany simulated the high pressures and temperatures which exist 200 kilometres deep inside the Earth. They found that the seawater which is present in the sediment at the ocean’s bottom reacts in the right way to form the salts which are present in the diamonds.

The study has been published in the journal Science Advances and it clears a major confusion about the way diamonds are formed. It was earlier thought that the salts within diamonds originated from the marine seawater. However, the research cleared that they originated from the marine sediment.


Diamonds are classified into gem diamonds and fibrous diamonds. Gem diamonds are fully composed of carbon in its purest form while fibrous diamonds contain the traces of elements such as sodium, potassium which can disclose a lot of information about the conditions in which their formation took place. Fibrous diamonds normally grow faster than gem diamonds which indicates that small samples of fluids are trapped during formation.

Samples of marine sediment were placed inside a vessel containing a rock called peridotite. It is the most common type of rock which is present in the mantle where diamonds are formed. Pressure and heat were increased and the adequate time to react with one another was given matching the conditions of the mantle.

At values of pressure lying between four and six gigapascals and temperatures in the range of 800 degrees to 1100 degree Celsius, which is equivalent to the depth of 120-180 kilometres inside Earth, salts were produced having the balance of sodium and potassium. It matched with the traces that are obtained inside diamonds.

Dr Michael Förster, lead author of the paper remarked that they have successfully demonstrated the sequence of steps which lead to the growth of diamonds and confirmed that the recycling of sediments in the ocean is responsible for it.


About the author: Kalpit Veerwal
Kalpit Veerwal is a second year Computer Science undergraduate at IIT Bombay. He is well known for being the only person to score 360/360 in JEE (Main). He is registered in the Limca Book of Records for the same. A blogger in his free time, he has also secured top ranks in various exams held in India and the world.

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