Compare open-pit mining and underground mining for diamonds, including typical cost, ore grade considerations, and risk profiles.

Compare open-pit mining and underground mining for diamonds, including typical cost, ore grade considerations, and risk profiles.

• A. Open-pit mining handles near-surface deposits with lower unit costs but greater surface disturbance.
• B. Underground mining targets shallower pipes with lower costs.
• C. Open-pit mining has higher ore grades than underground mining.
• D. Underground mining requires no blasting.

Answer: (D)