Cleavage
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In minerals and crystals, cleavage is the tendency to break at certain parallel planes in the crystal lattice . Cleavage is therefore a special type of fracture . The word is primarily used as a technical and craft term for rocks .
The crystal surfaces formed in the dissociation of minerals are often smooth atomically over large areas and reflect the light particularly well. Fissile abilities can be developed differently in different minerals and differ in the resulting fissile surfaces or levels as well as in the quality of their formation. It not only serves to classify minerals, but also allows conclusions to be drawn about the crystal lattice via the angles of the cleavage planes.
A behavior similar to cleavage is the so-called segregation , which, however, can often be traced back to a zonal structure of crystals, as is the case with tourmaline .
Types of cleavage
| designation | Column property | Examples |
|---|---|---|
| most perfect | finest leaflets can be split off | Mica , plaster of paris |
| perfectly | when smashed, you always get split bodies | Calcite , fluorite , galena , diamond (parallel to the octahedron surface) |
| Well | Both fissure and uneven fracture surfaces can be observed on fragments |
Amphibole group , feldspar , orthoclase , pyroxene group |
| clear | on the fracture surfaces there are subordinate planar gap separations |
Apatite , cassiterite , sulfur |
| indistinct | In addition to irregular fracture surfaces, smooth surfaces can
only be found in exceptional cases |
Corundum , magnetite |
| no cleavage | see fraction (mineral) | Diamond (perpendicular to the octahedron surface), quartz |
literature
- Paul Ramdohr , Hugo Strunz : Textbook of Mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 222-224
- Günther Mehling (Ed.): Natural stone lexicon . 4th edition. Callwey-Verlag, Munich 1993, ISBN 3-7667-1054-0