SORTING AND SELLING DIAMONDS.
Between the time that diamonds leave the mine and reach the cutter or industrial consumer, much preparatory work is necessary. Unlike other mining products, mostly homogenous, which can be refined to a standard purity and, therefore, command a standard price, diamonds occur in many thousands of different varieties and must be handled individually. Each rough stone must be classified and given a particular value before it is marketed.
When diamonds arrive in the sorting offices they will have been washed, but are otherwise in exactly the same condition as they were before removal from the surrounding rock or gravel. The first process in sorting is to remove the stones of industrial quality. There is no definite line of demarcation between a gem and an industrial diamond; some marginal stones exist which may be used either in industry or for jewellery according to the dictates of the market. The gem quality stones are then classified according to size, shape, quality (purity) and colour. The six shapes in which rough diamonds are found are stones, shapes, cleavages, maccles, flats and cubes. These six categories apply to stones of more than one carat. Below this weight there are two-divisions: melee, which are stones or shapes below a carat, and chips which are small cleavages or irregularly shaped crystals. Examing diamonds for quality, or purity, is the most exacting task for the sorter and the one which takes longest. Only a minute proportion of diamonds are entirely flawless; the majority possess one or more of the most common types of inclusion - spots of carbon, cracks and oxidization. Besides the size of the inclusions, consideration must be given to their position within the stone because this affects the cutting of a clean gem.
The grading of diamonds for colour similarly calls for expert judgement because such refinements of colour, however slight, will exert an influence upon the value of the polished gems. Ideally a diamond should possess no colour at all; it ought to resemble a piece of ice. Unfortunately the proverbial 'blue-white' is a rare object; most diamonds show a degree of colour, usually yellow or brown, which may extend from a slight tinge to a deeper shade. Diamonds are found in a wide range of colours but some of them such as pink, lilac-pink, green, dark blue, amber and canary yellow are very rare and command a value of their own. In the trade they are known as 'fancies'.
About 80 per cent of the world output of rough diamonds is handled or distributed through the Central Selling Organisation in London which was created by Sir Ernest Oppenheimer, the Chairman of De Beers, in the 1930s. Sir Ernest accomplished on an international scale what Cecil Rhodes had accomplished on a local scale; following a crisis in the industry between 1929 and 1930 he obtained the agreement of the producing concerns outside the control of De Beers to market their diamonds through a single channel. The Central Selling Organisation has developed its skills above all to maintain both stability in the diamond trade and confidence stability is necessary for the well-being of the industry, not because production is excessive or demand is falling, but simply because wide fluctuations in prices would destroy public confidence in a luxury item such as a gem diamond. Large quantities of diamonds are held in the form of jewellery by the general public. in diamonds as jewels of beauty and lasting value.