The method by which a rough diamond that has been mined from the earth is shaped into a finished, faceted stone. As a first step, cleaving or sawing is often used to separate the rough into smaller, more workable pieces that will each eventually become an individual polished gem. Next, bruting grinds away the edges, providing the outline shape (for example, heart, oval or round) for the gem. Faceting is done in two steps: during blocking, the table, culet, bezel and pavilion main facets are cut; afterward, the star, upper girdle and lower girdle facets are added. Once the fully faceted diamond has been inspected and improved, it is boiled in hydrochloric and sulfuric acids to remove dust and oil. The diamond is then considered a finished, polished gem. http://www.thediamondbuyingguide.com/diamondglossary.html Edit: hope this helps. Diamond Cutting In diamond cutting the stone is first cleaved or sawed to remove excrescences (outcroppings) or to break it into smaller stones. Cleaving is accomplished by making a groove in the surface in the direction of the grain, inserting a steel knife, and striking the back of the knife a sharp blow. The next process was formerly bruting, i.e., roughly shaping two stones by rubbing them against one another. In modern practice the stones are sawed with a revolving wheel coated on its rim with diamond powder, then shaped by inserting a holder, or dop, containing one diamond into a turning lathe that revolves it against a stationary diamond. The cutting of the facets and the polishing are done by a revolving iron wheel charged with diamond dust. After the facets are cut, the diamonds are cleaned and are ready for sale. http://www.bartleby.com/65/ge/gem.html

As a diamond is the hardest substance known to man, the only way to shape it is by using another diamond, so any cutting implements are coated with artificial diamonds.

I would just like to clarify something in Alatea's answer. She mentioned cleaving the diamond. Many minerals (diamond included) have planes of weakness inherent in the way the atoms are arranged. If you apply enough force on these planes of weakness, then the crystal will break along these planes. This is what a diamond cleaver does. He determines where these cleavage planes are in the diamond and how best to exploit them to give the best stone possible. (BTW, this is one of the reasons why you should not try scratching a piece of glass with you diamond to see if it is real. The stress you place on the stone in making the scratch could actually chip the stone along one of these cleavage planes. The other problem with this test is that most of the better diamond simulants are also harder than glass. So, that test doesn't prove anything.)

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Seeing as I cannot add to the great answers above, let me add a bit of levity: I put all the diamonds in the centre of the table, then I say "One for you, two for me...."

Hmm! The best cutters are in Amsterdam, probably would check them out