24 Feb

How are diamonds Mined?

Table of Contents

A freshly mined pink investment diamond from the argyle mine

Diamonds are mined all over the world, although different coloured diamonds are more abundant in some countries, than in others.

For example, purple diamonds are mainly mined in Russia, with occasional stones found in Canada, while most blue diamonds originated from the Cullinan Mine in South Africa. Over 90% of the world’s pink diamonds were mined in the Argyle mine in Western Australia.

Diamond mining involves a combination of art, science, engineering, and laborious work.

Generally, diamonds are taken from lamproite and kimberlite pipes, which are volcanic conduits transporting diamonds from the depths of the Earth’s mantle to the surface.

There are numerous ways of extracting diamonds from these pipes, including open-pit mining, underground mining, marine mining, and Alluvial mining.

How are Diamonds Mined?

Diamonds can be mined in several ways:

Open-pit mining is the most common method of diamond mining. It involves removing the top layer of soil and rock (called overburden) to expose the diamond-bearing layer, which is usually about 50-100 metres (160-330 feet) below the surface. This layer is then excavated, and the diamonds are extracted.

Underground mining is used when diamonds are found deeper than 100 metres (330 feet) below the surface. It involves excavating tunnels and shafts into the earth to reach the diamond-bearing layer.

Marine mining involves using specialised boats to extract diamonds from the ocean floor. It is mainly used in the coastal areas of Namibia and South Africa.

Alluvial mining is used to extract diamonds deposited in rivers, streams, and other bodies of water. It involves separating the diamonds from the sediment using various techniques, such as screening, panning, and sluicing.

To extract the ore from the mine it is detonated with explosives and loaded onto trucks and taken to a processing facility, where it is washed and sorted.

The fragmented ore is ground down into pieces no larger than 18 millimetres. The crushed ore is washed in a rotating drum called a scrubber and then put through two slotted screens that sort it into three different sizes.

It takes around 250 tons of ore to procure a single carat (or 200 milligrams) of a polished diamond of high quality.

Are diamonds found in coal mines?

Diamonds are not typically found in coal mines. Diamonds are created deep below the Earth’s mantle, in a region known as the lithospheric mantle, at depths of up to 100 miles (160 kilometres). Coal is a sedimentary rock and coal mines do not have the conditions necessary for diamond formation.

The diamond is formed when carbon atoms are subjected to extremely high pressures and temperatures. This process, known as diamond formation, typically occurs throughout millions of years.

The temperatures typically need to be approximately 2200 Fahrenheit and pressure of about 725,000 pounds per square inch to form. This intense heat and pressure, followed by a cooling process, gives diamonds a distinct hardness that cannot be found in coal or any other material.

All diamonds mined today have been brought to the surface through a volcanic eruption, during which diamonds are carried to the Earth’s surface in the magma and lava produced by volcanoes and cooled in the process.

Are old mine cut diamonds worth more?

Antique diamonds known as ‘old mine cuts’ were common in the 1800s and early 1900s and are typically identified by a square or rectangular shape, a tall peak, and a small top.

Old mine-cut diamonds and other antique diamonds have historically been sold for significantly less than modern cut diamonds. One reason is  because they are frequently recut into contemporary shapes, which wastes some of the original diamond.

It’s important to note that although the design is a factor in the price of a diamond, the 4 ‘C’s (Cut, Colour, Clarity, Carat) also contribute to its cost.

Where are pink diamonds mined?

90% of the world’s pink diamonds were found in the Argyle mine in Western Australia; originally Argyle diamond ore was excavated through large-scale open-pit mining, before being turned into a major underground block cave operation.

Pink diamonds are considered some of the world’s rarest and  most valuable, making many investors consider them a smart investment choice, particularly in times of market uncertainty.

If you are considering buying an Argyle pink diamond for investment, the best place to start is our Pink Diamond Guide

You can also contact our team of pink diamond experts here. 


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