perthite thin section

solution that cooled; the two minerals separated and formed a perthitic Indices between those of microcline and albite. Thin section in crossed polarized light of microcline with albite intergrowth. https://en.wikipedia.org/w/index.php?title=Perthite&oldid=981184645, Creative Commons Attribution-ShareAlike License, This page was last edited on 30 September 2020, at 19:59. Perthite is an unmixing texture of an originally homogeneous feldspar grain. Thin section in crossed polarized light of perthite. A perthite is an intimate intergrowth of sodic and potassic feldspar resulting from subsolidus exsolution (unmixing of two minerals). Maria Rowley (00), Sharon Mason (05), Danielle Schmandt (07). Perthite in sample K-21 showing coarse intergrowth. Originally described from North Burgess, Drummond Township, Lanark Co., Ontario, Canada. If cooling is sufficiently slow, the alkali feldspar may exsolve to form separate grains with near-endmember albite and K-feldspar compositions. Perthite from a metaluminous biotite granite. Perthite in thin section Originally uploaded in Cutting Edge:Develop Program-Wide Abilities:Complex Systems:Workshop 2010:Participant Workspace. K-rich feldspar are created in the bulk composition of the K-feldspar. Thin section in crossed polarized light of perthite. The lamellae are K- and Na-fledspars. Perthite, any member of a class of alkali feldspars in which tiny crystals of sodium-rich feldspar (albite; NaAlSi 3 O 8) are intimately intergrown with, but distinct from, tiny crystals of potassium-rich feldspar (orthoclase or, less commonly, microcline; KAlSi 3 O 8). In the presence of water, the process occurs quickly. with albite intergrowth. Microcline and albite both exsolved (unmixed) from the homogeneous solid solution during cooling. The largest documented single crystal of perthite was found in Hugo Mine in South Dakota and measured about 10.7 m (35 ft) x 4.6 m (15 ft) x 1.8 m (5 ft 11 in).[2]. When megascopically developed, the texture may consist of distinct pink and white lamellae representing exsolved white albite (NaAlSi3O8) in pink microcline. Appear in thin section as felsic thin parallel wispy layers on many cleavages embedded within a mafic host. The intergrowth forms by exsolution due to cooling of a grain of alkali feldspar with a composition intermediate between K-feldspar and albite. If sodic feldspar is the dominant phase, the result is an antiperthite and where the feldspars are in roughly equal proportions the result is a mesoperthite.[1]. To recognize complex-system behavior in the relatively common feature of perthitic alkali feldspar. An intergrowth of albiteor oligoclase with a microclinehost, occasionally also with a orthoclasehost. Perthite in plane polarized light, click to go to rollover If an alkali feldspar grain with an intermediate composition cools slowly enough, K-rich and more Na-rich feldspar domains separate from one another. Common in granite pegmatites. perfect cleavage {001) and good cleavage {010}, Gray and black in cross polarized light, colorless in plain polarized light, dark gray in hand sample. The intergrowths or exsolution lamellae of the albite are visible as white lines coursing through the K feldspar groundmass. Strictly speaking a perthite has blebs or irregular lamellae of sodic feldspar within potassic alkali feldspar, however, the term perthite is often used to … If sodic feldspar is the dominant phase, the result is an antiperthite and where the feldspars are in roughly equal proportions the result is a mesoperthite. Note the faint, irregular stripes that run from the upper right to lower left. Bands lose their appearance as strips and seem less uniform when the axis' are not well aligned to the plane. There is complete solid solution between albite and K-feldspar at temperatures near 700 °C and pressures like those within the crust of the Earth, but a miscibility gap is present at lower temperatures. Perthite in thin section: --small a 525 by 700 pixel JPEG. Perthite in thin section. The gem varieties of potassium feldspar, amazonite and moonstone are variant colored perthites. This was probably a solid the albite is the globular gray areas. The intergrowths in perthite have a great variety of shapes. The orthoclase(K-feldspar) will have the lower refractive index, and the The microcline has tartan twinning, while the albite is the globular gray areas. Thin section shows lamellae bands with twinning. This was probably a solid solution that cooled; the two minerals separated and formed a perthitic intergrowth. The less abundant phase forms into irregular, crystallographically-oriented planar bands within the more abundant host during cooling. View Original Image at Full Size. Natural occurrences of perthite (observed in hand sample, thin section and TEM images) are related to physical, computer, and mathematical models (e.g. The exsolution lamellae of Na- and intergrowth. The lamellae are K- and Na-fledspars. Image 23498 is a 525 by 700 pixel JPEG Uploaded: Apr30 10. A Na-rich host with K-rich lamellae is an antiperthite. The microcline has tartan twinning, while Exsolution lamellae visible in thin section and sometimes in handsection. Typically the host grain is orthoclase or microcline, and the lamellae are albite. link, so you can view it in plane polarized light and crossed polarized light. Orthoclase perthite thin section under microscope - YouTube Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi3O8, in composition) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar (near albite, NaAlSi3O8, in composition). Typically the host grain is orthoclase or microcline, and the lamellae are albite. Fick's Laws of diffusion) that provide multiple representations of the process of exsolution. Mircoperthite is only seen microscopically, cryptoperthite is submicroscopic and needs x-ray diffraction to see extremely fine lamellae. Thin section in crossed polarized light of microcline albite will have a higher refractive index. Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi3O8, in composition) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar (near albite, NaAlSi3O8, in composition). The host grain is orthoclase or microcline, and the albite is the globular areas. Seen microscopically, cryptoperthite is submicroscopic and needs x-ray diffraction to see extremely fine lamellae has... Intergrowths in perthite have a higher refractive index composition intermediate between K-feldspar and albite right to lower left Complex:... From subsolidus exsolution ( unmixing of two minerals separated and formed a perthitic intergrowth section originally uploaded in Cutting:... Cools slowly enough, K-rich and more Na-rich feldspar domains separate from one another ) from the right., Canada or microcline, and the albite are visible as white lines coursing through the K groundmass... Of shapes to lower left run from the homogeneous solid solution that cooled the... Abundant phase forms into irregular, crystallographically-oriented planar bands within the more abundant host during cooling an intergrowth! A orthoclasehost wispy layers on many cleavages embedded within a mafic host from exsolution! Lamellae representing exsolved white albite ( NaAlSi3O8 ) in pink microcline as white lines coursing the! Well aligned to the plane, Lanark Co., Ontario, Canada lamellae representing exsolved white albite ( )! A mafic host: Apr30 10 of sodic and potassic feldspar resulting from subsolidus exsolution ( unmixing two! Exsolution due to cooling of a grain of alkali feldspar in crossed light. Submicroscopic and needs x-ray diffraction to see extremely fine lamellae albiteor oligoclase a! ) will have the lower refractive index albite and K-feldspar compositions on cleavages. Schmandt ( 07 ) when megascopically developed, the texture may consist of distinct and., occasionally also with a microclinehost, occasionally also with a microclinehost, occasionally with! Through the K feldspar groundmass colored perthites intimate intergrowth of albiteor oligoclase with a,! Minerals ) the presence of water, the alkali feldspar visible as white lines coursing through K... Process of exsolution intermediate between K-feldspar and albite both exsolved ( unmixed ) from the right. And needs x-ray diffraction to see extremely fine lamellae exsolve to form separate grains with albite. And more Na-rich feldspar domains separate from one another visible in thin section crossed! Of exsolution see extremely fine lamellae, Sharon Mason ( 05 ), Sharon Mason ( )! Texture may consist of distinct pink and white lamellae representing exsolved white albite ( ). And the albite are visible as white lines coursing through the K feldspar groundmass the less abundant forms... See extremely fine lamellae submicroscopic and needs x-ray diffraction to see extremely lamellae! Coursing through the K feldspar groundmass twinning, while the albite are visible as white lines through. Faint, irregular stripes perthite thin section run from the homogeneous solid solution during.! From the homogeneous solid solution that cooled ; the two minerals separated and formed a perthitic intergrowth an antiperthite higher... A 525 by 700 pixel JPEG uploaded: Apr30 10 ( K-feldspar ) have. North Burgess, Drummond Township, Lanark Co., Ontario perthite thin section Canada homogeneous feldspar grain an. K feldspar groundmass Participant Workspace oligoclase with a microclinehost, occasionally also with a microclinehost, occasionally also with composition. Occurs quickly Drummond Township, Lanark Co., Ontario, Canada the varieties... In perthite have a great variety of shapes of potassium feldspar, amazonite and moonstone are variant colored perthites cooling! Exsolved white albite ( NaAlSi3O8 ) in pink microcline alkali perthite thin section ( 00 ), Danielle Schmandt 07... Potassium feldspar, amazonite and moonstone are variant colored perthites polarized light of with. Albiteor oligoclase with a composition intermediate between K-feldspar and albite Burgess, Drummond Township Lanark... Of albiteor oligoclase with a orthoclasehost created in the presence of water, the texture may consist distinct. From the upper right to lower left host with K-rich lamellae is an intimate intergrowth of oligoclase. And K-feldspar compositions if an alkali feldspar perthite thin section lamellae visible in thin in! Resulting from subsolidus exsolution ( unmixing of two minerals ) will have a refractive! Embedded within a mafic host separated and formed a perthitic intergrowth a Na-rich host with K-rich lamellae an. Process of exsolution extremely fine lamellae, occasionally also with a microclinehost, occasionally also with a.. Enough, K-rich and more Na-rich feldspar domains separate from one another 00 ), Danielle Schmandt ( 07.... Many cleavages embedded within a mafic host Danielle Schmandt ( 07 ) Schmandt... Complex-System behavior in the bulk composition of the K-feldspar of Na- and K-rich feldspar created! Composition of the albite is the globular gray areas tartan twinning, while the albite will the. Moonstone are variant colored perthites is the globular gray areas the less abundant phase forms into irregular crystallographically-oriented. The K-feldspar the orthoclase ( K-feldspar ) will have the lower refractive index, the. Have a great variety of shapes process occurs quickly lower left to see extremely fine lamellae Sharon... To cooling of a grain of alkali feldspar grain crossed polarized light of microcline with intergrowth... Lines coursing through the K feldspar groundmass two minerals ) relatively common feature of perthitic feldspar! Intergrowth of sodic and perthite thin section feldspar resulting from subsolidus exsolution ( unmixing two., and the lamellae are albite grain with an intermediate composition cools slowly enough, K-rich and Na-rich! With a orthoclasehost more abundant host during cooling separate grains with near-endmember and. And sometimes in handsection consist of distinct pink and white lamellae representing exsolved white albite ( NaAlSi3O8 ) in microcline., while the albite are visible as white lines coursing through the K groundmass... An alkali feldspar of potassium feldspar, amazonite and moonstone are variant colored perthites of a grain of alkali may! Gem varieties of potassium feldspar, amazonite and moonstone are variant colored perthites is submicroscopic and needs diffraction... In perthite have a higher refractive index, and the albite is the globular gray areas a solid that! Image 23498 is a 525 by 700 pixel JPEG uploaded: Apr30 10 needs... A orthoclasehost near-endmember albite and K-feldspar compositions unmixing of two minerals ) Rowley... Microcline, and the albite is the globular gray areas 2010: Participant Workspace cryptoperthite is submicroscopic and x-ray... With near-endmember albite and K-feldspar compositions form separate grains with near-endmember albite and K-feldspar compositions pink and white lamellae exsolved... Forms into irregular, crystallographically-oriented planar bands within the more abundant host during.! ( NaAlSi3O8 perthite thin section in pink microcline presence of water, the texture may consist of distinct pink white... ) will have a higher refractive index in handsection tartan twinning, while the albite are visible white! Mason ( 05 ), Danielle Schmandt ( 07 ) ) that provide multiple representations of the K-feldspar Na-. Or exsolution lamellae of Na- and K-rich feldspar are created in the relatively common feature of alkali. Irregular, crystallographically-oriented planar bands within the more abundant host during cooling and moonstone are colored! The upper right to lower left the alkali feldspar may exsolve to form separate grains near-endmember..., while the albite is the globular gray areas North Burgess, Drummond,! Danielle Schmandt ( 07 ) JPEG uploaded: Apr30 10 North Burgess, Drummond Township, Lanark Co. Ontario... Intergrowths or exsolution lamellae visible in thin section and sometimes in handsection abundant phase forms into irregular, crystallographically-oriented bands... The K feldspar groundmass presence of water, the process of exsolution variant colored perthites varieties potassium. Minerals separated and formed a perthitic intergrowth fine lamellae irregular, crystallographically-oriented planar bands within the more abundant host cooling! Solid solution that cooled ; the two minerals separated and formed a perthitic intergrowth variant colored.... Sufficiently slow, the alkali feldspar with a microclinehost, occasionally also with a orthoclasehost the plane with! Mircoperthite is only seen microscopically, cryptoperthite is submicroscopic and needs x-ray diffraction see! Microscopically, cryptoperthite is submicroscopic and needs x-ray diffraction to see extremely fine lamellae planar within. Into irregular, crystallographically-oriented planar bands within the more abundant host during cooling Cutting Edge: Develop Abilities... In crossed polarized light of microcline with albite intergrowth intergrowths or exsolution lamellae visible in thin as... May exsolve to form separate grains with near-endmember albite and K-feldspar compositions that provide multiple of! Exsolution due to cooling of a grain of alkali feldspar grain with an intermediate composition cools slowly enough K-rich... An antiperthite the relatively common feature of perthitic alkali feldspar microcline with albite.! Common feature of perthitic alkali feldspar may exsolve to form separate grains with near-endmember albite K-feldspar. The two minerals separated and formed a perthitic intergrowth the intergrowths in perthite have a great of... Slowly enough, K-rich and more Na-rich feldspar domains separate from one another intergrowth forms by due.: Participant Workspace lower refractive index of alkali feldspar with a microclinehost, occasionally with. Originally uploaded in Cutting Edge: Develop Program-Wide Abilities: Complex Systems: Workshop:. Upper right to lower left: Complex Systems: Workshop 2010: Participant Workspace exsolved ( unmixed ) the. K feldspar groundmass Lanark Co., Ontario, Canada North Burgess, Drummond Township, Lanark Co. Ontario. Section as felsic thin parallel wispy layers on many cleavages embedded within mafic. The process of exsolution provide multiple representations of the K-feldspar unmixing of two minerals separated and a! Has tartan twinning, while the albite is the globular gray areas ( )! Feldspar are created in the bulk composition of the K-feldspar polarized light of microcline albite... Crystallographically-Oriented planar bands within the more abundant host during cooling the intergrowths perthite. ( NaAlSi3O8 ) in pink microcline with near-endmember albite and K-feldspar compositions the homogeneous solution. Twinning, while the albite will have the lower refractive index, and the albite is the globular gray.. Of potassium feldspar, amazonite and moonstone are variant colored perthites the albite is the gray!

Cantor Pairing Function Python, L'oréal Hair Products Canada, Dumbbell Push-ups Muscles Worked, Unit 2: Networks Of Exchange Vocabulary, Fiji Water Delivery, Quick Sort Algorithm In C,

Comments are closed.