To the non-professional, an unpolished rough diamond appears to be very much like a dull piece of glass. Only when it is polished and facetted does it ascend to its full glory, displaying the sparking brightness and splash of colours for which it is famous. In the trade these are known as brilliance and fire.
 
From the time the diamond is transformed from a rough stone into a gem set in an item of jewellery, it has lost half of its weight. For centuries, because of a lack of understanding of the art of cutting, brilliance and fire was considered subordinate to weight. The individual credited for bringing about the change in approach was the Belgian Lodewijck van Bercken, who in the 14th or 15th century discovered the method of cutting a diamond with another diamond.
 
But before the cutting and polishing process begins, a thorough examination of the rough diamond is conducted. This is to determine how the largest possible polished stone or stones can be extracted, with the fewest number of impurities and best possible colour. It is a job that requires a thorough knowledge of diamond crystallography.
 
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