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how do they cut diamonds

Diamonds are cut by splitting, sawing, shaping, and polishing them with other diamonds and high‑precision tools, following the stone’s natural internal “weak lines” so it sparkles as much as possible.

Basic idea

  • Diamonds are the hardest natural material, so only diamond (diamond dust, diamond‑tipped tools, or another diamond) or specialized lasers are used to cut them.
  • Cutters take advantage of natural planes of weakness inside the crystal so it can be split and shaped without shattering.

Main steps

  1. Planning the cut
    • The rough stone is scanned and modeled with software to decide how to get the most carat weight and best shape out of it.
 * The plan balances beauty (proportions, brilliance) and value (how many stones, how big they’ll be).
  1. Cleaving or sawing
    • Cleaving: The cutter scores a groove along a natural weak plane, inserts a blade, and strikes it to split the diamond into pieces.
 * **Sawing:** If there is no good weak plane, the stone is cut using a high‑speed diamond‑coated or metal blade plus diamond powder, or a laser; the diamond powder is what actually does the cutting.
  1. Bruting (shaping the outline)
    • To make a round outline, the stone is spun on a lathe and ground against another diamond or a diamond wheel, creating the circular “girdle” around the middle.
 * This turns angular pieces of rough into a roughly round or shaped pre‑form ready for facets.
  1. Faceting
    • The cutter fixes the stone in a holder and presses it against a rotating metal wheel coated with diamond powder to grind each flat facet into place.
 * Angles and symmetry are controlled to maximize brilliance, fire, and scintillation (how much it flashes when moved).
  1. Polishing and finishing
    • The same diamond‑powder wheels are used with finer grits to smooth and polish each facet so the surface becomes mirror‑like.
 * The final steps include polishing the table (top), pavilion (bottom), culet (tip), and ensuring all facets are sharp and aligned.

Why only diamonds can cut diamonds

  • Diamond’s hardness means most other materials just wear away instead of cutting it, so cutting relies on diamond’s own hardness plus its internal brittleness along certain directions.
  • In practice, this is done with:
    • Diamond dust on metal blades and wheels
    • Other diamonds used as grinding partners
    • Lasers to slice or drill very precise shapes

Modern twists and “latest” context

  • Today, 3D scanning, computer modeling, and automated cutting machines help plan and execute cuts far more precisely than in the past, reducing wasted material.
  • Traditional hand skills are still vital, especially for high‑value stones, but many stages (like sawing and basic faceting) are now semi‑automated to improve consistency.

TL;DR: Diamonds are planned with computers, split or sawed along internal weak planes, rounded by rubbing against other diamonds, then faceted and polished on diamond‑powder wheels so the finished stone reflects as much light as possible.

Information gathered from public forums or data available on the internet and portrayed here.