Most people know that diamonds are made of pure carbon that has endured intense pressure from deep within the Earth’s mantle layer. We’re not talking SAT pressure, or public speaking pressure, we’re talking 5-year relationship, attending your girlfriend’s parent’s anniversary party pressure. Indeed, the amount of heat and pressure required for natural diamond formation makes an IRS audit on Wall Street seem like a cakewalk. But what exactly happens between the mantle and the mine? Here are the stages of growth in the life of a natural diamond.
1. Diamond Stability Zones
Diamond stability zones are stable interiors of continental plates that reside approximately 90 miles below the Earth’s surface in the mantle layer, where temperatures reach up to about 2000 degrees Fahrenheit. Suddenly, a crash landing in Botswana sounds rather lovely. The common belief that diamonds are formed from coal is a completely impossible theory due to the fact that coal is a sedimentary rock composed of plant debris and is rarely buried more than a mile into the Earth’s crust. In addition, the volcanic eruptions that passed through these diamond stability zones are believed to have occurred long before the emergence of plant life on the planet.
2. Kimberlite Pipes
The volcanic eruptions, which pass through the diamond stability zones to the surface, are responsible for the formation of kimberlite pipes. Kimberlite – named after Kimberley, South Africa – is a blue, igneous rock that often contains diamonds. Kimberlite pipes are carrot-shaped pipelines that are estimated to run up to 300 miles deep. The town of Kimberley is home to the Kimberley Mine, aka the “Big Hole” – arguably the largest hole excavated by hand. This mine became the enormous crater that it is today after the discovery of an 83.5-carat diamond in 1871, spawning the very first diamond rush.
3. Placer Deposits
When volcanic eruptions finally meet the Earth’s surface, diamonds are carried by their host rocks, kimberlite, and deposited en masse. Much of the kimberlite is carried away by streams and rivers and begins to undergo a sedimentary process. In this process the various mineral components are separated by gravitational forces and the diamonds are carried by stream sands into placer deposits. These placer deposits are prime real estate for those who are willing to sift through the dirt with an eye for the most valuable of prizes.