Diamond Rings

Diamond Rings – How Old Is Your Diamond?

Diamonds are created deep below the crust of the earth. Diamonds form under intense high pressure at depths of 140 to 190 kilometres below the earth's surface (sometimes even at 400 kilometres). The temperature required is between 900 - 1300 °C. The pressure and temperature must correspond for diamonds to form. The rock layers at those depths must contain some form of carbon. This perfect combination is found in the more ancient parts of the continental plates, where the crust is thicker and more stable. These regions of the lithosphere are called cratons, and they have survived the shifting of the continents for over 500 million years, some regions having remained stable for more than 2 billion years. The longer the diamond crystal remains in these perfect conditions, the larger it will grow.

Diamond Rings – Diamonds in the Earth

These diamond bearing rocks come up to the surface of the earth by the eruption of volcanoes. But, for the diamonds to reach the surface of the earth, a very particular and rare type of volcanic activity must occur. The magma must come up from below the depths where diamonds have formed (most volcanic lava erupts from a depth of 60 kilometres). In these eruptions, the mouths of the craters are usually very small and the lava does not get ejected fully. The cavity of these craters is characteristically long and narrow, which is why they are called "pipes". The molten lava that erupts does not create any diamonds itself; it is merely the conduit by which the diamond bearing rocks are brought to the surface of the earth. The magma in the pipes cools down over millennia, forming into an igneous rock called Kimberlite or Lamproite.

As the surface craters get weathered over the centuries, and the igneous rock breaks down into gravel and soil, wind and water erosion carry the diamond bearing mixture down into valleys, riverbeds and even to the seashore. The indestructible nature of the diamonds allows them to be carried very long distances before being deposited. The earliest diamonds were found in alluvial deposits. It was in the only in the 1870s that their true source was discovered and the mining of Kimberlite pipes begun.

Diamond Rings – Diamonds out of this World

The igneous rock, Kimberlite or Lamproite that transported the diamonds is only 50 million to 1,600 millions years old. The diamonds themselves have crystallised in the cratonic areas of the earth's crust and this makes them over 2 billion years old. Diamonds from South African mines have proved to be 3.3 billion years old. All natural diamonds are, at the very least, over a billion years old. How old is your diamond?

A meteorite that fell to earth in Canada, in January 2000 has revealed carbon particles in the form of nano-diamonds that scientists are calling "presolar". Researcher's date this rock at being 4.5 billion years old. This would predate the birth of our Solar System. Is it no longer farfetched to call the diamond "out of this world"?