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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 ...
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.
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]
In thin sections staurolite is commonly twinned and shows lower first order birefringence similar to quartz, with the twinning displaying optical continuity. It can be identified in metamorphic rocks by its swiss cheese appearance (with poikilitic quartz) and often mantled porphyroblastic character.
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 ...
In geology and materials science, a deformation mechanism is a process occurring at a microscopic scale that is responsible for deformation: changes in a material's internal structure, shape and volume. [1] [2] The process involves planar discontinuity and/or displacement of atoms from their original position within a crystal lattice structure.
Sanidine is the high temperature form of potassium feldspar with a general formula K(AlSi 3 O 8). [2] Sanidine is found most typically in felsic volcanic rocks such as obsidian, rhyolite and trachyte.