If a diamond is the hardest known substance , what is used to cut diamonds?

It seems paradoxical, but the very property that makes a diamond so exceptionally hard is the reason it is the primary tool used for its own shaping. Ranking as the hardest naturally occurring substance on the Mohs scale, a diamond can only be reliably scratched, cut, or polished by another diamond. The process is less like cutting with a knife and more of a meticulous grinding and shaping operation. Expert cutters use specialized tools coated with diamond dust or grit to transform a rough, unappealing stone into a brilliant, faceted gem. This intricate process requires a deep understanding of the diamond's crystal structure to achieve the desired result.

The journey from a rough stone to a finished jewel involves several key stages. Initially, the rough diamond may be split into more manageable pieces through cleaving or sawing. Sawing is accomplished using a thin blade whose edge is coated with diamond powder. Following this, a crucial step known as bruting or girdling takes place. In this phase, two diamonds are spun against one another, with their friction gradually shaping and rounding each stone to form their basic outline.

The final and most critical stage is polishing, where the gem's facets are created. This is done on a rotating wheel, called a scaife, which is coated with a paste of oil and fine diamond dust. As the diamond is pressed against the scaife, tiny facets are carefully ground and polished onto its surface. It is this precise angling of facets that gives a diamond its signature fire and sparkle. The entire process, from a rough stone to a polished gem, is a testament to both the unyielding nature of the material and the centuries-old craft developed to master it.