Now for the science bit…

Diamond in tweezers


Diamond is a mineral that is a crystalline form of carbon, the element ‘C’. It shares its chemical formula with graphite ‘C’. However, the carbon atoms in graphite are arranged in layers, and have weak bonds between the layers, making it soft and slippery. The carbon atoms in diamonds are arranged in tight 3D patterns with strong bonds in all directions which gives diamond its characteristic hardness.

Diamonds form between 90 and 120 miles under the surface of the earth, far our of reach of mining and they may remain there below the earth for millions and even billions of years until conditions within the earth’s mantle lead to violent eruptions that blast the already-formed diamonds and magma rapidly to the surface of the earth.  Some of these diamonds will be erupted, but others get stuck in the track of the eruption leaving conduits called pipes. This is where they may stay, fully formed, for millions more years until they are discovered and mined.  It’s these pipes which form the seams which are mined for diamonds and are much closer to the surface, although still a staggering depth of up to around 2 miles into the earth.

Often erosion of the Earth containing these pipes occurs which can carry diamonds into neighbouring rivers and streams, and even the ocean.  As the diamonds are heavy they stick to the bottom and are caught in small whirlpools. Deposits in rivers and streams are called alluvial deposits and they often contain higher quality diamonds than primary deposits mined from pipes because only the better specimens survive the pressures forced upon it with the water’s crashing actions against the rocks. Such deposits for example along the Namibian coast, contain in their yield about 95% gem quality diamonds.



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