Where it All Started:
Diamonds were delivered from the earth’s interior by volcanic eruptions. But as the magna percolated through the regions where the diamonds were stored, it carried some of them along a winding through cracks and crevices extending nearly 100 miles through rock toward the surface. In some cases the pathways led through layers of the Earth where the temperature was to high and the diamonds burnt up or turned into graphite.
In many cases the diamonds found themselves traveling within pressurized gas or water bubbles found inside the magma which protected the diamonds though the journey.
Diamond deposits:
Primary Deposits
Places where first brought to the surface known as Kimberlite or Lamproite pipes. These are pipes that once had diamond bearing magma flowing out of. (Kimberlite pipes are carrot shaped while Lamproite pipes are champagne flute shaped). Both pipes formed into three distinct sections:
1- Crater
A bowl shaped indentation in the Earth’s surface. Craters are usually created by magma fueled explosions.
2- Diatreme
The main body of a pipe located under the crater. These are mined for diamonds today.
3- Root
The lowest portion of the pipe.
Secondary Deposits
Places where the diamonds were carried by natural erosion of the Earth’s surface. The erosion happened over time and the diamonds were carried by water. These deposits are called “alluvial deposits” and they can be close to the pipes or miles away. Some river currents were so strong that diamonds where deposited in the ocean. These deposits are known as “marine deposits”. Some marine deposits naturally brought to the surface because the sea-level dropped.
Finding the Diamonds:
One story involving the most important diamond discovery was on accident by a young boy was cutting firewood. “It happened in the Cape Colony around the beginning of 1867. A teenager picked up a shiny pebble while he was cutting firewood. The pebble turned out to be a 21-carat diamond. This find was the beginning of a series of finds that sparked the diamond wealth in Africa.
But today, we are unlucky and rely on modern technology like airplanes, helicopters, and satellites along with finding the correct geology that was around ancient magma eruptions. But the search doesn’t end there. There are still more steps to take before any building is erected and finding a perfect formation usually doesn’t guarantee success. These next steps that follow the aerial discoveries are time consuming and extremely costly.
Surface Sampling
This step analyzes the chemistry of the pipe and if the magma came from the right depths which create diamonds.
Test Drilling
The area is split into workable grids to probe into the surface. This probing will help with the size and shape of the pipe.
Small Scale Mining
If all the earlier steps prove positive then some equipment is brought in to remove ore from the Earth. If any gem-quality diamonds are found then they are evaluated in size, quality and quantity.
All four steps will help determine the estimate of gem-quality carats found in that deposit and what the total worth would be. Even with all this time and money spent on these four steps, it only provides a small picture. The other picture is the total cost to erect buildings, cost of equipment, to build an infrastructure, water available, where would the workers and miners come from, climate pose any challenges, social or environmental impact and what are the political conditions like. These all play a major role in excavating the site.
Just a modern day example:
The Ekati Mine in Canada took roughly 17 to 18 years and $700 million dollars before any diamonds were dug out.
Mining Methods:
Alluvial Mining
Done by hand using a technique called “panning” or “screening”. For richer deposits machines that can dredge the bottom of the river, or the river could be re-routed to allow bulldozers or backhoes to do the digging.
Beach Mining
Building walls to keep the ocean off the beach allow bulldozers, earthmovers, and dump trucks to remove the earth.
Marine Mining
This is done in the open ocean using retired and converted oil vessels and platforms. Before any of these are put into place, wind, water currents and underwater-landscape all must be evaluated.
Pipe Mining
Size and depth vary because of erosion or the size of the eruption. There are two types of pipe mining:
Open pit
Is the most common of pipe mining. This is removing all of the non-diamond baring earth to get to the diamond baring ore. The open pit usually looks like a huge spiral of road way to the center. The deeper the spiral, the more measures are taken to protect the workers from a cave in.
Underground Mining
Is expensive and has many complexities. This type of mining starts off like an Open Pit mine but finds itself in a vertical tunnel with horizontal tunnels springing from it. This is only done if the pipe is rich enough in diamonds.
Recovery is the process of removing the diamonds from the ore and is generally automated to keep out the chance of theft happening. The ore is crushed by a machine that is designed to minimize the chance of damaging the diamonds. Then the diamonds and ore are sent into a scrubber which removes the dirt from the diamonds. The diamonds are then removed from the bottom with other minerals like garnet and zircon. Now the minerals and diamonds are placed on a greased belt and then the mixture of minerals are squirted with water. Because water doesn’t adhere to diamonds, the grease easily picks up the diamonds and washes the other minerals away.
South Africa
Diamonds were found for the first time in primary deposits, providing knowledge that led to future discoveries. Competition grew within many smaller miners which led to the formation of De Beers.
Angola, Botswana, Namibia, and D.R. Congo
Diamond discoveries began in the early 1900’s and continues today. Angola and Congo are politically unstable while Botswana and Namibia are prosperous and continue to grow. Botswana Orapa Mine could produce around 30% of the world’s diamonds. The Namibia’s Marine deposits could produce more than 1 billion carats.
Russia
Kimberlite pipes found in Sakha Republic which is near or above the Arctic Circle. Temperatures plunge to -100 degrees Fahrenheit during the winter months making it extremely hard to mine these pipes. But it is more than worth it because the output is close to or slightly over 20% of the worlds diamond supply. The Arkhangelsk region is the biggest untapped deposits in the world.
Western Australia
The world-renown mine, the Argyle Mine, is located here. Many of the diamonds are small in nature, but make up for their size in colors like pink, red, and champagne.
Canada Northwest Territories
After a decade or so of prospecting the Ekati Mine shot Canada to the top 10 of the most diamond producing countries. The mine went on-line around 1998 and is going strong today. By 2010 Canada could supply up to 10% of diamonds in value.
Antarctica
The geology is closely linked to South Africa, Australia, India and Brazil so many geologists believe this continent will be the last frontier of diamond discovery.
Producers by Carat Weight:
Botswana
Australia
Russia
South Africa
D.R. Congo
Canada
Namibia
Angola
Ghana
Liberia
Central African Republic
Brazil
Guinea
China
Sierra Leone
Ivory Coast
Venezuela