Diamonds…A piece of carbon that makes our hearts jump out of our bodies at the sight of it, with its beautiful brilliance and sparkle! But how much do we really know about diamonds? Here I am going to provide an insight into formation, mining, grading and different types of diamonds in a series of steps, to shed some light on the subject that is absolutely my personal interest.

224ct Rough Diamond
Image courtesy of M.A. Anavi Diamond Group

1st step: Formation of Diamonds

Diamonds are formed under extreme pressure (50 kilobars) and temperature (1,300 degrees) at depth of 125-200km in the Earth’s mantle over period of 1 billion to 3 billion years. Such extreme conditions change the molecular structure of carbons to a compressed lattice structure. That lattice structure is known as crystal lattice or rough diamonds, the very purest form of a diamond. Due to the changes in carbon atoms under the mentioned conditions, diamond is becoming a substance with highest hardness and thermal conductivity.

Diamond Crystal in a Kimberlite
Image courtesy of Geology for Investors

Rough diamonds are then carried to the Earth’s surface through deep origin volcanic eruptions which should originate at the depth where diamonds are formed, 150km or more which makes it a very rare occurrence. Diamonds are carried to the surface inside a greenish rock called Kimberlite. Kimberlite acts as a carrier to take diamonds to the surface of the Earth during eruptions which is also known as volcanic pipes.

Volcanic Eruption
Image courtesy of Science Magazine

To prevent their crystal structure to disintegrate into graphite, these eruptions thrust diamonds to the Earth’s surface at a great speed. Usually such eruptions create a massive explosion at the surface which deposit diamonds in a wide area. Kimberlite are often found in cratons (the surviving and stable part of continental crust), which is why diamonds are usually concentrated in northern Russia, Canada and southern Africa. A volcanic pipe that carries diamonds is known as primary source of diamonds. Secondary source of diamonds is known as the significant number of diamonds that scrape away from their kimberlite matrix, then accumulated in areas because of wind and water actions. Such deposits are called Alluvial and Marine as they are often discovered along the ancient shorelines. There are minor glacial deposits and due to hardship and investment requires to reach to such deposits they are not economically viable for mining companies to invest in.

Kimberlite Pipe (Big Hole) at Kimberley, South Africa
Image courtesy of University of Oxford