Tag Archive | mining

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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Are diamonds really a girl’s best friend…?

In the next few posts we’re going to take a closer look at diamonds.

Diamond in tweezers

 

Diamonds are notorious for their desirability and associated price tag, they are apparently a girl’s best friend, forever and a long standing essential in engagement rings.  Depending upon where you read the name comes from “Adamas” the ancient Greek word for “unconquerable” but other sources cite the name as meaning “indestructible.”  Either way because of its durability the diamond has been revered as far back as 800 B.C. in India which was the first major source of diamond and it’s easy to see why when you find out that they are the hardest natural substance found on Earth (10 on the mohs scale), impermeable to acids or solvents, with a melting point of an unimaginable (to my mind) 3547’C!

One of the more surprising facts about diamonds to my mind is the fact that whilst our high street and designer jewellers would be bereft without their bevy of brilliant cut beauties, the majority of mined, natural diamonds don’t actually get made into jewellery.

So what makes diamonds so desirable?  Of course, like most gemstones, they are rare, having been made over a billion years ago.  They are expensive to mine, it’s said that to produce one carat of diamond around 250 tons of earth will be mined.   They are expensive to facet, with around 50% of the original weight being lost during preparation.

Uncut diamonds were worn as talismans for protection in battle and to ward off illness, floods, thieves, evil spirits and even snakes, so depending upon your superstitious nature there may be nothing else that will do!

 

Picture from Wikipedia “Diamond”