From Rough to Polished

Of the millions of carats lifted from the earth each year, only about 20% are gem quality and worth polishing. Those that are can be shaped into almost anything — the round brilliant is only the most familiar of countless forms. A diamond, in the end, can be cut into whatever the mind can imagine. What turns a frosted, irregular crystal into that finished stone is a craft of three stages, each one committing the rough a little further toward light.

Cleaving or sawing

The work begins long before the first facet, with a single decision: which cut the rough will become. That choice made, the crystal is divided into a first rough shape — either cleaved by hand along the diamond’s natural grain, or sawn with a diamond-coated rotary saw or, today, a laser. It is the most consequential cut of all, because everything that follows is bounded by it.

Bruting

Next the stone is given its outline. Two diamonds are set rotating against each other in opposite directions and gradually round one another, grinding the rough toward its girdle silhouette. Diamond, the hardest material there is, can only be worked by diamond — and bruting is where that principle is most visibly at play.

Polishing

The final stage is itself three movements, and it is here the stone truly comes alive:

• Blocking — the first 17 or 18 facets are placed, establishing the stone’s main geometry.
• Brillianteering — the faceting of the remaining facets, the step that sets the fire and brilliance.
• Polishing — the finishing touch that brings every facet to a flawless, mirror-bright surface.