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n Bread may well be the staff of life, but thenreal stuff of life is carbon. Carbon is present in every known life formnon earth (it is the second most abundant element in your body, after oxygen,namounting to about 18%). What makes carbon so interesting is that exists innseveral forms, depending on the arrangements of the carbon atoms within ansubstance.
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| Pencil |
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nGraphite, for example, is carbon with the atoms connected in flatnplanes; it is black, opaque and soft, and is commonly found in pencils (which,ndespite the name, are not made of lead). Indeed, graphite gets its name fromnthe Greek word γράφω – grapho, ‘to write’, the root of such wordsnas graphology, autograph or biography. The atomic structure of graphite meansnthat the soft planes can easily be deposited onto a surface like paper –nimagine it like slices of bread in a sliced loaf, as each slice it taken away,nit is replaced by the next, identical, slice that lay below it. The propertiesnof graphite mean that it has a great many practical applications, from pencils,ncar brake linings, dry lubrication, metal casting moulds and batteries.
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| Coal |
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nInnanother form (or allotrope), amorphous carbon is found in coal, soot andnother impure forms – carbon takes its name from the Latin carbo –nmeaning coal. The atomic structure of amorphous carbon can be stabilizednby terminating the dangling-п bonds with hydrogen, producing hydrogenatednamorphous carbon (hydrocarbons), which are found in crude oil and petroleumnderivatives, certain waxes, and gases like methane, propane or ethylene.
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| Diamond |
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nAnthird allotrope of carbon occurs when the atoms are arranged in a face-centredncubic crystal structure – diamond. From the Greek αδάμας – adamas,n‘unbreakable’, diamond is known as the hardest material commonly available,nit rates 10 on the Moh’s scale of mineral hardness, and is used commercially inndiamond knives, saws and cutters, as well as a gemstone.
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| Moh’s Table of Hardness |
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nThe earliest diamondsnwere found in India, with a smaller number of stones discovered in Borneo, andnin Brazil in 1727, with more found in Africa from 1867, the first being thenEureka diamond.
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| The Open Mine at Kimberley |
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nThe African diamond rush began in 1870, when a 50-carat stonenwas found on a Jagersfontein farm, (the enterprising widow who owned this farmnrented out twenty square foot plots at £2 per month). When the famous Kimberleynmines were discovered in 1871, the leasing system of claims was superseded asndiamond-mining companies bought up the farms. In addition to the diamond mines,nrivers were also dammed, the water pumped out and the gravels dredged andnsorted.
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| Underground Diamond Mining |
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nRough diamonds are, at best, translucent and their beauty is notnevident until it is released by cutting the stone. Diamond cutting wasnintroduced into Europe from India, in 1295, and the technique was improved,nalmost two hundred years later, by Louis de Berguen of Bruges, who substitutednpolishing with corundum powder with diamond dust.
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| Diamond Cutting Office |
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nIn the seventeenth century,nVincenzio Peruzzi of Venice produced the first brilliant cut diamond, withnthirty-three facets, or faces, above the girdle of the stone and twenty-fivenbelow. The rough stone is held in a cement or soft solder mount as each facetnis cut and polished, and remounted for each individual facet, which arengenerally triangular or quadrangular in shape.
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| Diamond Cutting |
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nThe work is carried out over ansmall strong box, which serves to catch the resultant abraded powder andnfragments, known as bort. The process is both skilled andntime-consuming, particularly before mechanical methods were developed with, fornexample, the Regent diamond taking two years to cut in 1712 (at a cost ofn£5,000) and the Koh-i-noor was recut in 1862, taking thirty-eight days, atntwelve hours per day, costing £8,000 in labour.
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| Sorting the Silt for Diamonds |
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nBrilliant cut diamonds commandnthe highest prices, followed by Rose cut and Table cut gems, and the colour ofnthe stone also affects its value, with blue-white diamonds being the mostnvaluable, followed in order by blue, red, green, white, olive, black, firencoloured and yellow. A coal black stone of 350 carats, which was so hard it wasnimpossible to cut, was exhibited to great interest at the Great Exhibition innLondon, in 1851.
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| Diamond Cutting |
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nRough diamonds are examined by experts, who use their skill tondecide how the stone can best be cut with a minimum loss of size, beforenmarking it for sawing or cleaving to remove the excess areas. The part of thenstone which will provide the table is then decided on, this is thenlargest facet of the diamond, usually situated on the top of the stone, and thenfacets surrounding the table are then cut away, in a process called bruiting.
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| Diamond Polishing |
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nThe diamond is then polished, on a wheel, using a combination of diamond dustnand oil, until the required finish is achieved. There is no such thing as an‘perfect’ diamond, as they all contain minor imperfections, called flawsnor feathers, caused by intruding carbon atoms or minute cracks, but fornpractical purposes, ‘perfect’ stones are those that lack any flaws or spotsnthat can be seen by a person with ordinary sight using a watchmaker’snmagnifying glass.
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| Diamond Cutting Tools |
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nThe value of a diamond is said, popularly, to rest on the FournCs – colour, clarity, cut and carat. The carat is the weight of thenstone, set in 1907 as the metric carat of 200 mg of mass, but formerly fourngrains Troy weight, later set at just below four grains, the name thought toncome either from the Italian caratáre – to weigh with great care, or thenFrench caret – it is wanting, in reference to the tiny margin below thenfour grain measure.
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nThere is little evidence that folk etymology of the namenbeing derived from kuara, meaning a carob bean, is the true origin ofnthe term. The price per carat per stone is not linear, as larger stones arenrarer and thus demand a higher price per carat as the carat mass increases, andnprices are also affected by the demand for certain carat weight stones used innjewellery manufacture.
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nTomorrow – A Famous Diamond.
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