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Merohedral twinning occurs when the lattices of the contact twins superimpose in three dimensions, such as by relative rotation of one twin from the other. [8] An example is metazeunerite. [9] Contact twinning characteristically creates reentrant faces where faces of the crystal segments meet on the contact plane at an angle greater than 180°. [3]
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Pericline also refers to a doubly plunging anticline or syncline.. Pericline is a form of albite exhibiting elongate prismatic crystals. [1]Pericline twinning is a type of crystal twinning which show fine parallel twin laminae typically found in the alkali feldspars microcline. [2]
Orthoclase crystal twinning from the Organ Mountains in New Mexico. Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite. Typically, the pure potassium endmember of orthoclase forms a solid solution with albite, the sodium endmember (NaAlSi 3 O 8) of plagioclase.
A geological contact is a boundary which separates one rock body from another. [1] A contact can be formed during deposition, by the intrusion of magma, [2] or through faulting or other deformation of rock beds that brings distinct rock bodies into contact.
Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline. The chemical compound name is potassium aluminium silicate, and it is known as E number reference E555.
Plagioclase for example can be seen in the photo on the right as a clear mineral with multiple parallel twinning planes. The large blue-green minerals are clinopyroxene with some exsolution of orthopyroxene. Thin sections are prepared in order to investigate the optical properties of the minerals in the rock.
Twinning (making a twin of) may refer to: In biology and agriculture, producing two offspring (i.e., twins) at a time, or having a tendency to do so; In engineering and manufacturing, the creation of a digital twin or the synching of such twins; Twinning (cooperation) Afri Twin, an exchange partnership between schools in the United Kingdom and ...