Which direction is easier to polish?

• A. Along surface grain lines
• B. Parallel to crystal axes
• C. Against surface grain lines
• D. Perpendicular to cleavage planes

Answer: (C)

Polishing a diamond is easiest when you work against the surface grain lines. Those lines show the crystal’s natural microstructure; moving the abrasive across them rather than along them lets the tool cut through many tiny planes, removing material more evenly and quickly. It reduces the tendency to leave pronounced streaks or pull-out along a single line, producing a smoother, more lustrous surface. Directions that run with the grain tend to drag along the same micro-planes and can be slower with less uniform results, while directions related to cleavage planes raise fracture risk if not managed carefully. So, going opposite the surface grain lines gives the best combination of efficient material removal and a clean finish.