Which statement correctly defines a cleavage plane in diamonds?

Which statement correctly defines a cleavage plane in diamonds?

• A. A plane that cannot split the crystal.
• B. A plane perpendicular to a crystal face, where splitting cannot occur.
• C. Plane parallel to a possible crystal face, where a diamond can split cleanly when struck.
• D. A term for the color variation in a diamond.

Answer: (C)

Cleavage planes are planes of weakness in a crystal along which it tends to split. In diamond, these planes run parallel to certain crystal faces, so when hit along that direction the bonds along that plane break and the crystal divides cleanly, producing flat surfaces. This is why the statement describing a plane parallel to a possible crystal face where a diamond can split cleanly when struck is the correct description. The other ideas don’t fit because a plane that cannot split describes no cleavage; a plane perpendicular to a crystal face isn’t where cleavage occurs; and color variation has nothing to do with how a diamond fractures.

Cleavage planes are planes of weakness in a crystal along which it tends to split. In diamond, these planes run parallel to certain crystal faces, so when hit along that direction the bonds along that plane break and the crystal divides cleanly, producing flat surfaces. This is why the statement describing a plane parallel to a possible crystal face where a diamond can split cleanly when struck is the correct description. The other ideas don’t fit because a plane that cannot split describes no cleavage; a plane perpendicular to a crystal face isn’t where cleavage occurs; and color variation has nothing to do with how a diamond fractures.