Coning is commonly done on round-shape diamonds. What is its main purpose?

• A. To reduce potential damage to strained stones
• B. To improve symmetry in marquise stones
• C. To increase luminosity
• D. To shorten bruting time

Answer: (B)

Coning is all about achieving symmetry in the final cut. When a round diamond is coned on the bruting wheel, the goal is to shape a uniform, well-centered edge that provides a consistent reference for subsequent polishing and faceting. This careful preparation helps ensure the weight is evenly distributed and the outline remains balanced, which is especially important when later converting that rough into other shapes—like marquise—where symmetry along the length and across the girdle is critical for a pleasing, well-proportioned result. So, the main purpose is to support better symmetry in shapes such as marquise cuts, rather than to affect luminosity, shorten bruting time, or reduce damage to strained stones.