Rough is the technical term to describe a diamond once retrieved from the ground and prior to being cut. In photograph #1 we see a classic example of an octahedral piece of rough. Much evaluation precedes any cutting. The cutter must decide, first and foremost, whether the diamond is “gemmy” (gem quality). Being “gemmy” is the first major audition that a piece of diamond rough must go through. If it’s “gemmy” it will be cut into a diamond for jewelry. If not, it gets tossed into the industrial grade pile. In photograph #2 we get a peak at a typical reject. It’s opaque; brown with nitrogen and heavily included. If it’s lucky it will end up at the end of a drill bit somewhere.
Once a diamond has passed the “gemmy” audition the cutter must decide the best way to attack it. There are two main types of cutters; those that cut for weight/profit and those that cut for beauty. Sometimes the two go hand in hand. The weight cutters focus on size as the most important factor almost to the exclusion of clarity, color and cut. The true master cutters place it last. In diagrams #3, #4, & #5 we can see some of the options available in cutting one single piece of rough.
In diagram #3 the cutter is contemplating cutting one large diamond from the single piece of rough. As a rule a weight cutter will retain 50% of the rough in a finished diamond while a quality cutter settles for one third. In diagram #4 the cutter is abandoning cutting one large stone with possibly major internal flaws (inclusions) for two medium sized possibly higher quality rocks. In the last diagram (#5) the cutter wastes nothing! He not only goes after a medium to large diamond but tries to slip in a little mini one as well.