Cleavage (crystal)

Cleavage is a mineral’s tendency to break along flat planes where atomic bonding is weaker. Its directions and quality reflect the crystal’s internal structure.

Crystal lattice: A repeating three-dimensional arrangement of atoms, ions, or molecules in a crystalline solid. Cleavage planes follow directions through this repeating atomic arrangement.
Cleavage plane: A crystallographic plane along which a mineral tends to split. It is the specific surface orientation underlying a mineral’s cleavage.
Mica: A group of sheet silicate minerals that readily separates into thin, flexible sheets. Strong cleavage in one direction lets mica split into exceptionally thin layers.
Mineral identification: The process of determining a mineral’s identity from its physical and chemical properties. Cleavage direction and quality help distinguish minerals with similar appearances.
Chemical bond: An attraction that holds atoms or ions together in a substance. Cleavage occurs where bonds resist separation less than they do in other directions.
Cleavage direction: The orientation of a mineral’s preferred plane of breakage relative to its crystal structure. A mineral may have one or several distinct preferred orientations.
Halite: The mineral form of sodium chloride, commonly known as rock salt. Its three perpendicular cleavage directions produce cubic fragments.
Petrology: The study of rocks, including their origins, composition, and geological history. Mineral cleavage contributes to identifying rock-forming minerals in specimens.
Miller index: A notation that identifies the orientation of a plane in a crystal lattice. Miller indices describe the crystallographic orientations of cleavage planes.
Cleavage quality: A description of how readily and smoothly a mineral splits along a cleavage plane. Quality names the visible strength and regularity of the property.

Linked from 22 pages