From Rough to Polished: How a Laboratory-Grown Diamond Is Cut in Surat

A laboratory-grown diamond doesn't come out of the reactor sparkling. A CVD crystal emerges as a flat, square-ish block with a rough, often dark outer layer; an HPHT crystal looks like a small cube-octahedron. Turning that rough into a brilliant gem is the same skilled work used for natural diamonds, and Surat is where most of the world's diamonds, natural and laboratory-grown, get that treatment.

1. Cleaning and inspection

The rough is cleaned and examined for growth features and inclusions. For CVD material, the outer graphite layer and edges are removed.

2. Planning

Using 3D scanning and planning software, the planner maps the crystal and works out how to cut the most valuable polished diamond, or diamonds, from it: which shape, which size and how to place any inclusions where they will be cut away or hidden.

3. Sawing and laser cutting

Lasers cut the rough according to the plan, separating it into the pieces that will become individual diamonds.

4. Bruting (shaping)

For round diamonds, the stone is spun against another diamond or shaped by laser to create the round outline, called the girdle.

5. Faceting

This is where the sparkle is born. Skilled polishers place each facet on a rotating polishing wheel coated with diamond powder, the only material hard enough to polish diamond. A round brilliant has 57 or 58 facets, each placed at a precise angle so light enters, reflects and returns to the eye.

6. Final polish and quality control

Stones are checked for symmetry, polish and proportions. Larger stones go to independent laboratories such as IGI for grading, where they may be laser-inscribed with their report number.

7. Sorting and matching

Finally, stones are sorted by size, shape, colour and clarity. For melee, careful matching is what makes a halo or eternity band look uniform.

Craft handed down

Surat's diamond cutters have passed this craft down through generations. The arrival of laboratory-grown diamonds has created new work for these skills, and new opportunities for the city.

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