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Twinning results when different parts of the crystal break their isometric symmetry along a different choice of axis. This is typically polysynthetic twinning, which enables the crystal to maintain its isometric shape by averaging out the displacement in each direction. This produces a pseudomorphic crystal that appears to have isometric symmetry.
Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula Na Al Si 3 O 8. It is a tectosilicate. Its color is usually pure white, hence its name from Latin, albus. [5]
Plagioclase displaying cleavage. (unknown scale) In volcanic rocks, fine-grained plagioclase can display a "microlitic" texture of many small crystals. Plagioclase (/ ˈ p l æ dʒ (i) ə ˌ k l eɪ s, ˈ p l eɪ dʒ-,-ˌ k l eɪ z / PLAJ-(ee)-ə-klayss, PLAYJ-, -klayz) [4] is a series of tectosilicate (framework silicate) minerals within the feldspar group.
Grains are commonly elongate with a tabular appearance. May contain lamellae which formed from exsolved albite. Twinning: Typically displays albite twinning and pericline twinning. This combination leads to a grid pattern, hence microcline displays gridiron twinning. Can also display carlsbad twinning, simple twins, or lack twinning altogether ...
The side of the diagram between calcite and sillimanite has a point added for anorthite (calcium feldspar), corresponding to an equal mixture (by mole percentage) of the two components. This forms pure anorthite. Likewise, points are added for clinopyroxene and garnet and the diagram is divided into subtriangles, as depicted in the accompanying ...
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] The twinning results from a structural transformation between high temperature and low temperature forms. [3]
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Diagram of a catalytic reaction, showing the energy level as a function of the reaction coordinate. For a catalyzed reaction, the activation energy is lower. In chemistry, a reaction coordinate [1] is an abstract one-dimensional coordinate chosen to represent progress along a reaction pathway.