Diamonds form 75-120 miles below the earth’s surface where the high temperature and high pressure melt rock and forces the carbon atoms to form into new rock crystals. Conditions necessary to form diamonds are tenuous because if the temperature rises or the pressure drops then the diamond crystals may melt or even dissolve.
Even when diamonds crystals form, they are still located far below the earth’s surfaces. It takes a violent volcanic eruption, called kimberlites that propel the diamonds up through the earth’s crust before they have a chance to be crushed and pulverized on any other path to the surface. Diamonds are extremely hard which means they are highly resistant to scratching but they can break when hit at the right angles with force as rocks shift in movements over time in the earth’s crust.
Geologists estimate that diamonds arrived at the surface via kimberlites from 45 million to 2.5 billion years ago. Many of the diamonds are still locked up in the softer kimberlite (sometimes called blue ground) and lamproite rock in the carrot-shaped pipes. Because these types of rock are softer than the surrounding rocks, the forces of nature over millions of years eroded away some of the material leaving the harder diamond crystals to settle in river beds and eventually wash out to sea. Diamonds moved and deposited due to erosion are called Alluvial Deposits.
A young researcher is exploring the process involving diamonds deep underground. The results of his research are being presented as part of the Fresh Science national competition. The diamond industry, in particular the Australian diamond industry, hopes that a better understanding of the force that move diamonds to the surface will point to other areas with diamond deposits.
The Australian diamond industry is in decline because the known deposits and existing mine production are both decreasing. Australia has vast expanses of land where diamonds might be found if better tools can be developed to identify potential sites.