Diamond Formation

The glitter of diamonds, the perfection of their facets and their scintillating fire always makes one wonder that how did these shining beauties come to existence? Diamonds are formed under certain precise conditions in the deep interiors of the earth. These sparkling fruits of nature are believed to be more than billions of years old and form under the stable continental plates. In this post we will unearth the procedure of diamond formation.

The formation of diamonds takes place under extreme conditions. Diamonds form mostly in the mantle which is below the surface layer of the earth at a distance of approximately 150 Kms. When carbon crystals are subjected to a temperature of 1050° C and a pressure of 45000-60000 Kilobars, is when the process of diamond formation begins. These conditions are not present uniformly in the layers of the earth. These conditions mostly exist under the stable continental plates. These stable parts are called cratons.

 

CRATONS

It is a fairly common belief that when a person or an object is subjected to immense pressure and difficulties they either they crack or come out victorious. The same is with the diamonds they undergo extreme heat and pressure in the interiors of  the earth but a slight change in the conditions can lead to formation of graphite.

 

GRAPHITE

There are two types of diamonds – P Type and E Type. P type diamonds are formed with the help of peridotitic rocks and E type are formed with the assistance of eclogitic rocks.  Peridotite and eclogite are referred to as source rocks as the diamonds form in these igneous rocks. These rocks exist under the earth in a molten state and they continuously emit carbon. The carbon atoms under the immense heat and pressure of the earth’s interiors start locking with each other. If the conditions are accurate diamond crystals start forming.

PERIDOTITE

Diamonds formed in the mantle are brought up to earth’s surface by the deep volcanic eruptions. These eruptions break the mantle and bring the diamonds to the surface. The rocks which transport the diamonds are kimberlite and lamproite. Kimberlite and lamproite are formed in the molten magma in the mantle.  The magma expands as it heats up and it passes through a fracture in the crust. While passing through a fracture it might come in contact with a diamond deposit and carry the diamonds along with it. The magma then continues to rise and the pressure decreases. With the decrease in pressure magma is able to travel at a very high speed of about 300 Kms/hour. At this stage some chemicals start to vaporise into carbon dioxide and water vapour. The speed of magma along with release of gases leads to an explosion. At this very point kimberlite pipes are formed. These pipes are where the majority of diamonds are found.

 

KIMBERLITE PIPE

Any change in vaporisation and the speed of magma can result in formation of graphite. The kimberlite or lamproite then solidifies creating a diamond rich deposit. This is what most of the diamond miners hunt for.

Diamonds go through a lot before one sees them glittering in a store’s display. They undergo extreme heat and pressure and are brought to the earth by violent eruptions. For years together they trapped there until unearthed by man. Thereafter, they are cut and polished and that’s when one sees the real beauty of diamonds.  And that is why it is said, to have an understanding of diamond formation is extremely important not only from technical aspects but also because so that one can appreciate this unique process and also how rare are fine gem quality diamonds.