Multiple choice general knowledge

The second hardest substance known to man is??

  1. Diamond

  2. Boron Nitride (BN)

  3. Calcium

  4. Iron
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Boron Nitride (BN) in its cubic form is the second hardest known substance after diamond. Diamond ranks first on the Mohs scale of mineral hardness, while cubic boron nitride ranks second. Calcium and iron are significantly softer metals.

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