- foliation
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/foh'lee ay"sheuhn/, n.1. the act or process of putting forth leaves.2. the state of being in leaf.3. Bot.a. the arrangement of leaves within a bud.b. the arrangement of leaves on a plant.4. leaves or foliage.5. Print. the consecutive numbering of the folios or leaves, as distinguished from pages, of a manuscript or book.6. the total number of such leaves.7. Petrol. a form of lamination produced in rocks by metamorphism.8. ornamentation with foliage, or an arrangement of foliage.9. Archit.a. ornamentation with foils.b. ornamentation with representations of foliage.10. formation into thin sheets.11. the application of foil to glass to make a mirror.[1615-25; FOLIATE + -ION]
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Planar arrangement of structural or textural features in any rock type, but particularly that resulting from the alignment of constituent mineral grains of a metamorphic rock along straight or wavy planes.Foliation commonly occurs parallel to original bedding, but it may not be obviously related to any other structural direction. Foliation is exhibited most prominently by sheety minerals, such as mica or chlorite.* * *
▪ geologyplanar arrangement of structural or textural features in any rock type, but particularly that resulting from the alignment of constituent mineral grains of a metamorphic rock of the regional variety along straight or wavy planes. Foliation often occurs parallel to original bedding, but it may not be ostensibly related to any other structural direction. Foliation is exhibited most prominently by sheety minerals, such as mica or chlorite.Regional metamorphic rocks are usually subdivided into schist, slate, and gneiss on the basis of grain size and foliation type. The schists, for example, exhibit strong foliation with partings along well-defined planes of medium-grained micas or hornblendes. The gneisses (gneiss), which are characteristically rich in feldspar and quartz, tend to be coarse-grained and less distinctly foliated. They do not split, or cleave, along their planes as schists do. A few contact-metamorphic rocks are foliated, but most, such as hornfels and granulite, tend to be granular.* * *
Universalium. 2010.