Diamonds in HistoryDiamond Mining

Creation

It took millions of years for diamonds that exist today to be created in the depth of the Earth. It is known that the formation of diamonds requires extremely high pressures and temperatures. It is also known that the conditions necessary for diamond formation no longer exist today in nature. What remains largely unknown is how exactly the process of turning carbon atoms into very precise and stable crystals of diamond takes place. While there exist theories based on the process of artificial creation of diamonds, no indisputable proof exists that the same process occurs at the Earth's core.

The most common theory goes as follows. Somewhere 150-200 km deep under the surface of the Earth, inside an active volcano, where pressure is 70 thousand times higher than at see level and temperatures reach 1300°C, carbon dioxide reacts with other compounds and as a result crystals of pure carbon are created. Most crystals are octahedrons (have 8 surfaces) as shown on the left, but some have 6 or 12 surfaces. Certain stones do not follow such structures because they were broken into fragments on their way to the surface from the depth where they were formed.

The molten mass that produces the crystals is not pure, and diamonds often include trace amounts of different elements. When this happens, atoms of that element take the place of some of the carbon atoms in the crystal lattice, slightly changing the physical properties of the resulting diamond. The addition of nitrogen for example, will make the crystal yellow. The more nitrogen, the more accentuated the colour becomes. In fact, most diamonds on the market include trace amounts of nitrogen, but in such small quantities that the colour is barely noticeable. Traces of boron make the diamond blue, while pink and red colours are due to differences in the bonding between the atoms, not the external trace elements. It is notable that not all elements can successfully displace carbon in a diamond crystal. Boron, carbon and nitrogen are similar enough from a chemical point of view that they can replace each other in a crystal, although in very small quantities — traces. Creation of diamonds is an extremely slow process that requires constant conditions to form a clean crystal with uniform shape and colour. The creation of coloured diamonds depends on such precise and rare conditions, that it is not suprising that only a handful of them is found every year.

Thousands of years may pass before a volcanic eruption ejects these diamonds onto the surface. Low quality stones have a tendency to break on their way up, as an eruption is a very violent event, but those that make it to the top, are often high quality and ready to be cut for jewellery.

Diamonds in HistoryDiamond Mining