The Unique Challenge of Diamond Cutting
Diamonds are the hardest natural material known, registering a perfect 10 on the Mohs scale of mineral hardness. This exceptional property means no other substance can scratch a diamond, making it incredibly resilient. This inherent hardness presents a significant challenge when shaping a rough diamond.
Traditional cutting tools, typically made from hardened steel or other robust metals, are ineffective against a diamond’s atomic structure. These materials would dull or break before making any impression. Transforming a raw diamond into a polished gem requires a fundamentally different approach than cutting other minerals or metals. Its strong atomic bonds resist conventional separation methods.
The Material That Cuts Diamonds
The unique challenge of cutting a diamond is overcome by utilizing the very same material: diamond itself. This is possible because while diamonds are universally hard, their hardness is not entirely uniform across all crystallographic directions. A diamond possesses microscopic “hard” and “soft” directions, which are subtle variations in atomic bonding strength depending on the angle of approach.
Diamond cutting tools exploit these slightly softer directions within the rough diamond. Diamond dust, composed of tiny diamond particles, serves as the abrasive agent. These particles are often embedded into the surfaces of cutting wheels or saw blades, creating a tool that can effectively abrade and shape another diamond. The collective action of these microscopic diamond edges allows for gradual material removal.
The process also leverages cleavage planes present in diamonds. These are specific atomic planes within the crystal structure where bonds are relatively weaker. Skilled diamond cutters can utilize these planes to split a diamond with a precise impact, a technique known as cleaving.
Methods of Diamond Cutting
The journey from a rough diamond to a faceted gem involves several precise methods, all relying on diamond-on-diamond interaction. One primary technique is sawing, where diamond-impregnated saw blades divide a larger rough diamond into smaller sections. Modern advancements also incorporate laser cutting, which uses a high-powered laser to vaporize the diamond material along a predetermined line, offering extreme precision.
Cleaving is another method, involving splitting a diamond along its natural cleavage plane. A cutter makes a small notch in the diamond, then delivers a sharp, precise blow with a specialized tool to cause the diamond to split cleanly. This method requires an intimate understanding of the diamond’s internal structure to ensure a successful and controlled separation.
Bruting, also known as girdling, is the process of shaping the diamond’s outer edge, called the girdle. This is achieved by mounting two diamonds on spinning spindles and rotating them against each other. The abrasive action of one diamond against the other gradually grinds away material, creating a perfectly round and symmetrical outline for the future gem.
Finally, polishing brings out the diamond’s brilliance and fire. This stage involves using a scaife, a rotating cast iron wheel coated with a mixture of olive oil and fine diamond powder. The diamond is held against this spinning wheel, and the abrasive action of the diamond powder creates the precise facets and smooth surfaces that define a finished gemstone.