Diamond Processing

View of Venetia Processing Plant View of Venetia Processing Plant

Processing diamondiferous ore and Diamond Value Management, the strategy that guides our operations, are inextricably linked. Both aim to maximise the value and life of our diamonds.

The method we choose to release diamonds from their surrounding ore - usually kimberlite - depends on the properties of both diamonds and of the host rock.  


We break and fracture the ore (the technical term for this is comminution) using crushing and milling processes to reduce the particles fed into our automated facilities and "liberate" diamonds.


Diamonds are heavier than the material that surrounds them. Once the ore has been crushed to a manageable size, we mix it with a slurry made of finely ground ferrosilicon prepared to a specified density. In a method known as Dense Medium Separation (DMS) that exploits the relative densities of different materials, we apply centrifugal force to the mixture to separate a diamond-rich concentrate. Downstream, we recover the ferrosilicon for re-use.

At this point, we usually repeat the crushing and concentration stages to free more, usually smaller,  diamonds.   

A piece of kimberlite with an exposed diamond A piece of kimberlite with an exposed diamond
The process of recovering diamonds from kimberlite begins The process of recovering diamonds from kimberlite begins


Diamonds have several remarkable properties that we're able to exploit to recover them from the stream of prepared concentrate. They emit light under X-rays enabling us to detect and separate them.  They repel water and are attracted to grease. When we mix the concentrate with water and pass it over a grease belt, the diamonds adhere to the grease. And they fluoresce under the laser sorters we use to further concentrate the  processing stream.

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