A jeweler would use another diamond to cut a diamond.
Another diamond.
The only substance capable of cutting diamond would be it's self. Now, Lasers can also cut diamonds. But I don't consider lasers a substance.
Another diamond is the only substance hard enough to cut diamond.
Only another diamond is hard enough to cut a diamond. Diamonds are the hardest mineral, scoring a 10 on the Mohs scale of hardness.
Diamond. Curious, perhaps, that the hardest substance known can be shattered - but not scratched or cut.
One of the hardest substances on earth, only a diamond is hard enough to cut other diamonds. It is possible only because the hardness of diamond varies widely according to the direction in which one is trying to cut or grind. Therefore a harder diamond is used to cut one that is slightly softer (due to impurities).
My favorite diamond cut for an engagement ring would probably be the Ascher cut.
Because diamonds are the hardest substance on earth known to man, and therefore would probably make an accurate cut. A glass cutter marks the cut on the glass using a diamond-tipped tool, then taps one side of the cut with a rubber mallet, to separate the pieces.
Its easy to cut a diamond if you know how to do it but its very hard to get the angle right, but they're the hardest substance on the planet.
If the diamond is a round cut, the measurement would be 7.4 mm at the girdle. If the diamond is of another cut, the measurement would be different.
Diamonds are used to cut other diamonds, since no other substance is hard enough to cut a diamond, except a diamond. You could find stories related to this phenomenon in India, and Antwerp, where most diamonds are cut and polished. You can read a chapter from Edward J Epstein's online book, below, where there are stories of diamond cutting.
Any website that sells anything with diamonds would have pictures of cut diamond items. There are also many books that would have great pictures of cut diamond items as well.