Image by Jackson Cadenhead. Triclinic System: The group of silicate minerals called the Plagioclase felspars having Albite (NaAlSi 3 O 8) and Anorthite (CaAl 2 Si 2 O 8) as the end members show interesting types of twinning. Plagioclase A photomicrograph of a plagioclase crystal under cross polarized light. polysynthetic twinning (usually uncountable, plural polysynthetic twinnings) A type of contact twinning, typically observed in plagioclase, in which the composition surfaces are parallel to … It has a tendency to format polysynthetic twinning (Fig. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or ‘record-groove’ effect. Click here to see list of references, authorities, sources and geographical terms as used in this glossary. Sunstone samples S1 and S2 contain platy inclusions of opaque grains, which show a strong preferred orientation. Albite twins give plagioclase the characteristic polysynthetic twinning that is often visible as fine striations in hand specimen and as stripes in thin section. It also demonstrates that plagioclase, as a series, can be nearly any color. The plagioclase crystal shows a distinct banding effect called a Polysynthetic twinning. Special features of plagioclase crystallization occur from the magma and lava. The twins are, however, generally of repeated polysynthetic type. This twinning is the most characteristic identifying feature of plagioclase, and makes its identification easy when present. Two grains at the bottom centre of the image also show simple Carlsbad twinning. The plagioclase crystal shows a distinct banding effect called polysynthetic twinning. Plagioclase in hand samples is often identified by its polysynthetic twinning or 'record-groove' effect. 02-jun-2018 - Plagioclase in XPL, showing polysynthetic twinning Labradorites Lab1, Lab3 and Lab4 are aggregates of multiple grains. (unknown scale) General Category … Wikipedia. Thin Section: low relief, lack of color, biaxial character, and polysynthetic twinning distinguish pla. Repeated twinning Ang plagioclase sa mga sample ng kamay ay kadalasang nakikilala ng polysynthetic crystal twinning o epekto ng 'record-groove'. It is also possible for crystals to exhibit compound twinning in which two twin laws are expressed simultaneously. In feldspar: Crystal structure …common kinds of twinning—those designated Carlsbad twinning and albite twinning—are shown in the figure.Carlsbad twinning occurs in both monoclinic and triclinic feldspars; albite twinning occurs only in triclinic feldspars.Albite twinning, which is typically polysynthetic (i.e., multiple or repeated), can be observed as a set of parallel lines on… Orbit navigation Move camera: 1-finger drag or Left Mouse Button Pan: 2-finger drag or Right Mouse Button or SHIFT+ Left Mouse Button Zoom on object: Double-tap or Double-click on object Zoom out: Double-tap or Double-click on background Zoom: Pinch in/out or Mousewheel or CTRL + … successive twinning of more than two individual crystals according to the same twin law and parallel composition planes such as plagioclase feldspars. The plagioclase feldspars can range in color from colorless to white to greenish yellow and even flesh red. Synonym of: polysynthetic twinning. 2: Phase diagram for Or-free plagioclase feldspars at atmospheric pressure. o Albite Law - As described above, plagioclase (NaAlSi3O8 - CaAl2Si2O8) very commonly shows albite polysynthetic twinning. perpendicular to the b-axis. As stated above, plagioclase feldspars. Polysynthetic twinning – occurs when three or more individuals are repeated alternately on the same twinned plane. In other cases of pyroxenes, Orthodome (101) is the twinning plane. See hand sample 1844 as a good example of what to look for. Name : From the Greek plagios – “oblique” and klao – “I cleave” in allusion to the obtuse cleavage angles of the good cleavages. They have a vitreous, pearly luster. The Albite twin law {010} indicates that the twins make a form, the faces are parallel to the mirror plane (010), i.e. Albite-Carlsbad: the two halves of the image also show simple Carlsbad twinning as a series, can nearly. 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