How Diamonds Are Processed
The vast majority of the world’s diamonds are found in volcanic pipes know as kimberlites. These kimberlites carry diamonds from deep in the earth’s crust, to the surface of earth where they solidify and host the diamonds within. As these are subterranean, extracting these diamonds requires the mining of this host rock, or diamondiferous ore. This ore is mined from the earth in smaller pieces, and delivered to a process plant for extraction.
Extraction of diamonds from host rock typically occurs in several stages. The first four of these stages is often repeated multiple times in order to isolate and recover different diamond sizes, the first run will typically produce larger stones, and when repeating smaller and smaller stones can be recovered.
Stage 1 : Primary Crushing
- The larger pieces of host rock are crushed into smaller pieces.
Stage 2 : Secondary Crushing
- These smaller chunks need to be crushed further to a more manageable size.
Stage 3 : Dense Medium Separation Mixing
- This rock is now added to a mixture of other materials, typically Ferrosilicon, and water to form a suspension of solid particles, or slurry.
Stage 4 : Cyclonic Separation Plant
- The Slurry is now sent for dense medium separation through cyclonic separation. In this process the slurry is fed into a machine that spins at rapid speed. The materials in the slurry have different densities and weights, by spinning the slurry in specifically shaped chamber, the relative densities of each of the materials is exploited and the components containing diamond can be separated for further processing.
Once cyclone separation has been completed, processors are left with a concentrate of materials more likely to contain diamonds within. These host materials are now sent for further scanning, and separation.
Stage 5 : Hydrophobic Grease Separation
- Diamonds are known to exhibit certain specific traits that help machines perform analysis, and separate diamonds for further processing.
- The first of these is that diamonds are hydrophobic, and attracted to grease. By placing the materials on vibrating grease tables and automated grease belts. Water is sprayed onto the vibrating table or bely as a diamond concentrated slurry passes over it. As the diamonds are hydrophobic, but stick to grease, the diamonds will stick to certain points allowing the other materials in to travel on down into the waste stream.
Stage 6 : X-Ray Fluorescence Separation
- Diamonds are also known to emit Fluorescence when exposed to X-rays. This allows an x-ray fluorescence separator, to scan a stream of particles from the a concentrate as it falls through a beam of x-rays, and activate photo detectors that trigger air deflectors to separate the diamond.
Stage 7 : Boiling and Collection
- The last step in recovery is to collect the separated materials and add them to a boilers to remove the grease from the previous steps. Once this has been completed there material is made up of more than 50% raw diamond. This is then dried and sent for sorting and cutting.
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