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Question of the Day · Science

Sunday, September 20, 2026

What is the hardest natural substance on Earth?

Hints

  1. It forms deep beneath Earth's surface.
  2. It is made entirely of carbon.
  3. It is commonly used in jewelry and cutting tools.
Reveal the answer

Answer: Diamond

Diamond is the hardest naturally occurring substance, thanks to the strong bonds between its carbon atoms.

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