Argyle’s open pit diamond mine, which ceased operations in August 2013, produced more than 800 million carats of diamonds over its 28-year life. The Argyle diamonds continue at depth and an underground block cave mine has been developed as the safest and most economical way to reach deep into Argyle’s ore body.

Block cave mining involves undercutting the ore body and allowing it to break up or ‘cave’ under its own weight, removing the need for explosives or blasting. The technologically sophisticated underground operation at Argyle is the first block cave mine in Western Australia and one of only two operating in Australia.

The Argyle underground mine is a challenge both in size and complexity. There are around 40 kilometers of tunnels. The main thoroughfares in the underground network are four tunnels – two to carry vehicles, one for ventilation and one for moving ore. There are two large underground crushers and conveyor belts transport the ore from deep in the mine to the surface.

Today, the Argyle processing plant is one of the most efficient in the world. It is capable of processing up to 11 million tonnes of ore per annum.

Once extracted, the diamond bearing ore is taken to a processing plant where it is crushed, scrubbed and screened. The particles of ore at that point are between 1 and 30mm in size. A technique called dense medium separation (DMS) separates the diamonds and other heavy minerals from the less dense waste ore. The diamonds can then be separated from the other minerals in the concentrate using an x-ray sorter. Under x-rays, diamonds fluoresce. The flashes of light that they emit trigger a blast of air that blows only the diamonds out of the concentrate. The diamonds are then cleaned, washed and weighed, ready to be sorted and valued for sale.