Diamonds are formed from crystallized carbon and are the only gemstone known to be made up of a single element. It sounds simple, but in fact, the formation of diamonds is a complex and lengthy process. Once the diamonds have formed, things do not get much simpler. Diamonds typically are found embedded in carrot-shaped pipes of volcanic rock called kimberlite, and harvesting the gems means separating them from this rock. Because the ratio of diamonds to kimberlite can be very low, harvesting usually is done on a large scale, and heavy machinery is necessary in the early part of the process.
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How to Separate Diamonds from Kimberlite
Load the material extracted from the mine into a crusher and gently smash the volcanic rock, being careful not to use enough pressure to crush the gems.
Place the crushed rock and gem material into rotating drums filled with water. The water will disintegrate the small bits of volcanic material, leaving only diamond crystals intact.
Add ferro-silicon sand to the mixture of water and ore to further separate the diamond crystals from the volcanic material. Remove the ferro-silicon with a magnet, and empty out the water. Small diamonds and a few diamond-laden chunks of heavier rock should be all that remain.
X-ray any heavy pieces of kimberlite-encrusted materials that remain. Diamonds glow under x-rays and can be located and separated easily.