How are Diamonds Mined?

It seems strange that a mineral entirely made up of carbon has become one of the most sought-after jewels in the world, namely the diamond. After all, carbon is found in our most basic materials and equipment, such as the graphite in our pencils, which hardly seems luxurious.

It’s the formation of these carbon atoms that makes the diamond so unique: there are only few select places on the planet where the temperature-pressure balance is ideal for the formation of these precious stones.

Diamonds form naturally in the earth’s mantle, roughly 150 km’s below the surface, and are brought to the surface by lava. Whenever a volcanic eruption occurs, diamonds are pushed through the earth’s surface in chunks of mantle.

They are then mined by breaking down the mantle to extract the diamonds in their rough form. There are several mining methods depending on the geological location. Let’s take a look at how diamonds are mined around the world.

Pipe-Mining

One of the richest diamond mines in the world can be found in Botswana, where up to 11 million carats of diamonds are mined on a yearly basis.

These open mining pits are created by digging down towards the volcanic crater and exposing the kimberlite pipes which tend to hold the diamonds.

Once the kimberlite is exposed, the pit’s ore is blasted and the loosened rocks are hoisted onto transport trucks, and the extracting process is ready to commence. Open-pit mining sites can be recognized by their unusual, terraced structures leading down to a big crater exposing the kimberlite pipes.

Underground pipe-mining counts as one of the most dangerous and physically challenging professions in the world, with temperatures reaching up to 45°C below ground.

The deepest diamond mines in the world can be found in TauTona and Savuka in South Afrika, reaching depths of 3, 900 meters below the earth’s surface.

1. Two tunnels are built – one directly above the other – through which the miners reach the kimberlite pipes.
2. Once the ore is located it is blasted, and then funnelled into the deepest tunnel.
3. The broken ore is collected by the miners and packed onto transport wagons which are brought back to the surface where the extracting process takes place.

Marine Mining

Marine-mining or deep-sea mining, first became popular in the sixties, following the publication of J.L. Mero’s Mineral Resources of the Sea. Several nations sent out research vessels to explore the claims of limitless supplies of nickel, cobalt and other metals that are found in manganese nodule deposits, but with little result.

It was soon decided that marine mining would be too costly to be profitable in the diamond and gemstone trade, with an estimated $650 million US dollars having been spent between 1960 and 1980.

This decade has seen a rise in deep-sea mining, using specialised ships equipped with a crawler that is inserted into the seabed. The gravel extracted from the seabed is sucked up through flexible pipes and loaded onto the ship where the diamond extraction takes place.

Other ships use huge drills with which to excavate the diamonds. Both methods have been questioned in relation to their negative impact on the ocean’s ecosystem.

Placer Mining

Placer mining also referred to as alluvial mining, is one of the oldest gold and diamond mining methods.

These methods are applied for alluvial deposits in stream beds, which often house gemstones that have been moved by the stream’s flow.

• Alluvial deposits form when the ore washes off its ore due to changing weather conditions.
• Miners use a large metal pan to extract the stream bed’s gravel along with a generous amount of water and then agitate the mixture allowing the gold or diamonds to settle at the bottom.

Placer mining dates all the way back to ancient Rome, but these days, placer sites have become more elaborate, facilitating the work of the miners. A large wall is usually erected on site, forcing water to pool in one area. This allows miners to work through specified areas in a systematic manner.

Although most mines rely on pipe-mining these days, various mines in Australia and Venezuela still follow the traditional placer mining methods, keeping costs as low as possible.

Now you know how diamonds are mined have a look at the end product used in the Purely Diamonds range of jewellery here.