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Geology & Earth Sciences vocabulary · Rocks & Minerals

Cleavage

Meaning in geology & earth sciences, with examples

/ˈkliːvɪdʒ/nounCommon term

In geology & earth sciences, cleavage means: The tendency of a mineral to break along flat, smooth planes of weakness in its crystal structure. Mica splits into thin sheets because of its perfect cleavage.

In Turkish: dilinim, klivaj

How it is used

Described by quality (perfect, good, poor) and number of directions: one in mica, two in feldspar, three in calcite and halite. Minerals without cleavage, like quartz, show fracture instead. In metamorphic rocks, 'slaty cleavage' is a rock texture.

Example sentences

  1. Feldspar has two cleavage planes at nearly right angles.

  2. Calcite breaks into rhomb-shaped pieces because it has three directions of cleavage.

Common collocations

  • perfect cleavage
  • cleavage plane
  • two directions of cleavage
  • slaty cleavage
  • cleavage and fracture
  • mineralA naturally occurring, inorganic solid with a definite chemical composition and an ordered internal structure, such as quartz, calcite or feldspar.
  • hardnessA mineral's resistance to being scratched, measured on the Mohs scale from 1 (talc) to 10 (diamond). It is one of the first tests used to identify minerals.
  • crystalA solid in which the atoms are arranged in a regular, repeating pattern, which often gives it flat faces and a typical shape.
  • quartzA hard, common mineral made of silicon dioxide (SiO2), usually clear, white or grey with a glassy lustre. It has a hardness of 7 and no cleavage.

More terms: Rocks & Minerals

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