Which era introduced continuous rotary motion and a cast-iron polishing wheel that shifted cutting toward faceting?

• A. The 15th century
• B. The 16th century
• C. The 14th century
• D. The 13th century

Answer: (B)

The key idea is how technological advances enabled diamond cutting to become a facet-driven process rather than just rough shaping. In the 16th century, cutters began using continuous rotary motion with a cast-iron polishing wheel. This combination gave a stable, repeatable way to grind and polish facets around the stone, turning the cutting process into a systematic, symmetrical operation rather than one-off, hand-guided work. The wheel provided a durable, smooth polishing surface, and the rotating motion allowed many facets to be formed consistently, which is the shift that defines faceting. Earlier periods didn’t have this reliable rotary tooling, so the move toward multiple, precisely angled facets really takes hold with tooling from the 16th century.