Cleavage plane is defined as which of the following concepts?

Cleavage plane is defined as which of the following concepts?

• A. A plane parallel to a crystal face where a diamond can split cleanly when struck
• B. A plane perpendicular to a crystal face where a diamond can split cleanly when struck
• C. A curved surface of the crystal
• D. A line of weakness along which a crystal fractures

Answer: (A)

Cleavage planes are flat, parallel planes of weakness in a crystal lattice along which the mineral tends to split cleanly. They run parallel to crystallographic planes, which means they align with the crystal faces you see in a well-formed crystal. In diamond, the clean, flat surfaces you can obtain when it splits occur along these planes that are parallel to crystal faces, so describing a plane that is parallel to a crystal face captures the essence of cleavage. This is what allows a diamond to break with smooth, straight surfaces when struck along those directions. The other options describe a plane perpendicular to a crystal face, a curved surface, or a line of weakness, none of which define cleavage planes.

Cleavage planes are flat, parallel planes of weakness in a crystal lattice along which the mineral tends to split cleanly. They run parallel to crystallographic planes, which means they align with the crystal faces you see in a well-formed crystal. In diamond, the clean, flat surfaces you can obtain when it splits occur along these planes that are parallel to crystal faces, so describing a plane that is parallel to a crystal face captures the essence of cleavage. This is what allows a diamond to break with smooth, straight surfaces when struck along those directions. The other options describe a plane perpendicular to a crystal face, a curved surface, or a line of weakness, none of which define cleavage planes.