Alkali feldspar extinction

Feldspars - UCL Earth Science

Repeat the procedure on a number (6-10) of grains to determine the maximum extinction angle. Use the maximum extinction angle to determine the composition of the plagioclase from the Michel-Levy composition chart.. ALKALI FELDSPARS. Include compositions between KAlSi 3 O 8 and NaAlSi 3 O 8. In this system, different ordering of Si and Al on tetrahedral sites changes symmetry of structure Alkali Feldspar (Click PPL image to show labels) Orthoclase in a granite from Fionnphort, Isle of Mull. Large orthoclase (alkali feldspar) crystal with string perthite visible even in PPL M401 Alkali feldspar, orthoclase Norway A fragment of opaque, pale grey alkali feldspar. Two sets of good cleavage at right angles, with a pearly lustre on the cleavage faces. M402 Alkali feldspar, orthoclase Shap, Westmorland Porphyritic granite. Large phenocrysts of pink feldspar, two sets of cleavage at 90°, simple twinning. Also white plagioclase feldspar, quartz and biotite Feldspars in some 'fresh' igneous and metamorphic rocks can be clear and silvery in appearance but the great majority of alkali feldspars and many plagioclase feldspars are to some degree turbid, and translucent (Fig. 1) or opaque, even in small fragments. Turbidity in feldspars is caused by myriads of tiny, often fluid-filled 'micropores,' produced by reactions with aqueous fluids in the upper crust Alkali feldspars can often be distinguished from plagioclase feldspars because most grains of the latter exhibit albite twinning (see above Crystal structure ), which is manifested by parallel lines on certain cleavage surfaces, whereas grains of alkali feldspars do not. This criterion is not, however, absolute; some plagioclase feldspars are not.

Alkali Feldspar GeosecMIA - GEOSEC Slide

Extinction angles that reported will be the maximum possible acute angle, and thus different orientations of the minerals could produce extinction angles from 0 to 45 o. Other Properties, as discussed abov Extinction: parallel to cleavage: Length fast/slow: no slow or fast length: Diagnostic features: Distinguishable from microcline by a lack in gridiron twinning. Distinguishable from sanidine by a larger 2V x. Other characteristics: Low negative relief; Alters to sericite or clay (commonly) Reference Plagioclase grains are completely unaltered. Alkali feldspar occurs along fractures, adjacent to quartz inclusions and as thin trails along cleavage and twin planes (black arrows Fig. 3b). Alkali feldspar porphyroclasts constitute 9% of the protomylonite and range in size from 20 µm to 1.8 mm, with an average grain size of 350 µm

Alkali feldspar (orthoclase) - Grains typically 2-4mm long, subhedral to anhedral, dirty looking due to alteration. Many display a microperthite texture. Plagioclase feldspar. - Grains typically 1-4mm long, subhedral, characteristic lamellar twinning. Many of the grains look dirty under plain polarised light, and have high birefringence speckles. Some crystals of alkali feldspar are invariably clouded and stained by pale reddish brown materials (a mixture Of iron oxides and clay minerals). They also exhibit clear colorless dentatc albite rims and vcinlcts. crystals show wide variation in size and abundance to 25%. Of the mode); is a local gradation feldspar syenile to alkali-feldspar granite Feldspar constitutes an important family of rock-forming minerals. It is an aluminium silicate combined with varying proportions of calcium, sodium and/or potassium. Large gem quality crystals of feldspar are rare but do occur as labradorite. In the Cheviot pluton, feldspar forms small grains varying in size from microscopic to about 4mm in length

Alkali feldspar · 1A Collection

In plagioclase, the contacts between twins tend to be sharper, and the twins do not pinch and swell. ·K-feldspar is similar to quartz, but quartz lacks cleavage , lacks twinning, does not alter, exhibits undulatory extinction, and is uniaxial. Microcline in a Granite Many of the alkali feldspar phenocrysts contain irregu-larly shaped cores of another alkali feldspar or plagioclase. These cores are generally visible in crossed polars through abrupt discontinuities in extinction angles, but are most clearly revealed in backscattered electron images (see be-low) because the alkali feldspar overgrowths contain dis Yellowish quartz is an acceptable sacrifice, because you can still infer that it's quartz by its extinction patterns. The quartz in this biotite gneiss is a great example. Had the person who made the thin section ground the sample down any farther, many of the feldspars would have been lost

Feldspar - an overview ScienceDirect Topic

The microstructures of alkali feldspars crystalli-sed at lower temperatures are relatively less known. TEM observations of twinning and exsolution texture in a hydrothermal and two pegmatitic microclines (TIBBALS & OLSEN, 1977) extended the study of K-feldspar microtextures below the temperature of the monoclinic-triclinic transformation Augite is a clinopyroxene. Clinopyroxenes and orthopyroxenes are easily distinguished in thin section by their extinction angles: clinopyroxenes have inclined extinction, and orthopyroxenes have parallel extinction. Physical Properties. Chemical formula. (Ca,Mg,Fe,Na) (Mg,Fe,Al) (Si,Al) 2 O 6

Quartz is a common and often essential mineral in a wide variety of sedimentary, metamorphic and igneous rocks. It is always nearly pure SiO 2. Keys to identification are:colorless nature, first order white-gray interference colors, and undulatory extinction. It also lacks cleavage , twinning and alteration About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators.

Feldspar - Identification of specific feldspars Britannic

  1. Aug 30, 2020 - This Pin was discovered by Bryn Mawr College Mineralogy. Discover (and save!) your own Pins on Pinteres
  2. goniometer speed). For the talline inclusions of plagioclase and quartz. The host d-value measurements the reflections of accompanying rock is coarse grained where the alkali feldspars have quartz (JCPDS #33-1161) were used as an inner stand- the largest size. ard
  3. eral. Anorthite is the calcium endmember of the plagioclase feldspar
  4. Weakly shocked alkali feldspar mainly developed irregular fractures and undulatory extinction. Note that the Raman -lines 210 and 765 are missing in the w -shocked feldspar, and an additional line at ≈ 150 appears. The shock pressure for the w -shocked feldspar was estimated to be between 5 and 14 GP

A zircon U-Pb age of 120.2 ± 1.7 Ma has been dated by ion microprobe in situ for the Laoshan A-type granite in eastern China. Fossil 231Pa excess has been inferred to explain the observed 207Pb-208Pb decoupling for alkali feldspar. In order to reconcile the apparent paradox of fossil 231Pa excess for alkali feldspar rather than for zircon, two hypothetical mechanisms for a water. Feldspar is the most abundant mineral in the Earth's crust and is widely distributed in rocks. It is also one of the most common minerals in meteorites. Shock-metamorphic features in feldspar are widely used to calibrate the temperature and pressure of shock events and can also provide clues for searching for impact craters on Earth. In this study, shocked alkali feldspars in the lithic.

Extinction Angle. Extinction angle is the property that involves determining the angle between the a crystallographic direction as exhibited by a crystal face or cleavage and one of the principal vibration directions. So, we expect to find Al-rich minerals in aluminous schists, like garnet, muscovite, alkali feldspar, biotite, and an Al 2. Alkali Feldspar in Detail . Alkali feldspar has the formula KAlSi 3 O 8, potassium aluminosilicate. The formula actually is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify it there. This mineral is often called potassium feldspar or K-feldspar. undulatory extinction and the alkali-silica reaction. Proceedings of the 9 th international conference on. (760-780°C), the alkali feldspar was enriched in sodium. The mixing of the partial. Basically, the two properties which make feldspars useful for downstream industries are their alkali and alumina content. On those elements we can distinguishThree families: 1) Feldspatic sand: with an alkali content (Na2O+K2O) < 6% or alumina content (Al2O3) < 8% 2) Pegmatite: with an alkali content (Na2O+K2O) >6% and alumina content (Al2O3. feldspar are bent, a few shows broken bands and most of the quartz grains show undulose or wavy extinction. (Figure 9a, 9b, 9c and 9d) Under the microscope, quartzofeldspathic layer show ductile shear deformation. The following facts are supported the ductile deformation: (1) Some augen texture of feldspar grains are surrounded by quartz ribbons

The alkali feldspars are distinguished by their cross-hachured extinction patterns. Plagioclase, in contrast, has very straight twin planes - polysynthetic twinning - and the twin sets go extinct at different angles giving plagioclase a black and white striped appearance Each alkali feldspar crystal has both pristine and turbid areas. different extinction position to that of the pristine areas and is often Albite-twinned. Small alkali feldspar crystals in the. Moonstone is a name given to a gem material that consists of very thin, alternating layers of orthoclase (an alkali feldspar) and albite (a plagioclase feldspar). Some specimens of labradorite exhibit a schiller effect, which is a strong play of iridescent blue, green, red, orange, and yellow colors when moved under a source of incident light Alkali feldspars occur in magmatic, metamorphic and sedimentary environments. Mineral parageneses involving alkali feldspar, and in particular the chemical compositions cal extinction under polarised light. Plates with polished (010) surfaces were produced (Fig. 1) Neoproterzoic, anorogenic, A-type granites of Dhiran area of Malani Igneous Suites is made up wholly of peralkaline-peraluminous alkali feldspar granites and is composed of K-feldspar, quartz, alkali amphibole, plagioclase, biotite and accessory minerals are iron oxides, monozite, zircon, apatite, and annite. This granitoid is associated with acid volcanic and minor basic volcanic-plutonic and.

Plagioclase Feldspar (Click PPL image to and also concentric growth zoning is seen in crystals near extinction. Width of field of view: 12mm. Albite (polysynthetic) twinning is an indicator of plagioclase, quartz shows no twinning, and the alkali feldspars usually only show carlsbad, and also some perthitic exsolution texture.. Alkali Feldspar Group > Feldspar Group Name: Name given in 1830 by Johann Friedrich August Breithaupt to a reddish to brownish feldspar from Arendal, Norway, and a feldspar with bluish schiller from Stavern (formerly Fredrichsvärn), Norway, from the Greek μικρός (little) and κλινειν (to incline), in allusion to the small departure. when measuring extinction angles in a-normal determinations. Alkali feldspar: May be either orthoclase or microcline and is commonly perthitic in slowly cooled plutonic rocks. Note any inclusions, alteration, twinning, etc. Quartz: Look for evidence of deformation (undulose extinction) and resorption However, in the alkali feldspars 1/4 of the Si +4 ions are replaced by Al +3 and in the plagioclase feldspars 1/4 to 1/2 of the Si +4 ions are replaced by Al +3. This allows for the cations K + , Na + , and Ca +2 to be substituted into void spaces to maintain charge balance

Feldspar - bnm.wik

  1. OPTICAL PROPERTIES (POTASH & ALKALI FELDSPARS) Properties Orthoclase Microcline Anorthoclase Color Colorless, Cloudy Relief Low - Moderate Twinning Carlsbad Cross - hatched Very Fine Cross - hatching Interference Color Grays of First Order Extinction Max. 21˚ Max. 15˚ ≈ 2˚ Optic Sign Biaxial (-ve
  2. Feldspar - Feldspar - Uses: Feldspars are used widely in the glass and ceramics industries. Alkali feldspars are more commonly used commercially than plagioclase feldspars. Albite, or soda spar as it is known commercially, is used in ceramics. The feldspar-rich rocks larvikite and a few anorthosites are employed as both interior and exterior facing slabs
  3. ALKALI FELDSPARS: ORDERING, COMPOSITION AND OPTICAL PROPERTIES by Shu-Chun Su F. Donald Bloss, Co-chairman Paul H. Ribbe, Co-chairman Geological Sciences (ABSTRACT) For the entire alkali feldspar series, !t1 (total Al content in the Ti sites, a quantitative measure of structural state or Al,Si long-range ordering) can be closel
  4. erals of alkali‐feldspar (53~56 vol.%), plagioclase (3~6 vol.%), quartz (32~35 vol.%), and biotite (5 vol.%). The alkali‐feldspar is mainly composed of microcline and perthite, with a size range from 0.5 × 1 to 1 × 2 mm. Evident pelitization and sericite alteration can be found in the alkali‐feldspar
  5. eral(s)
  6. The chemical composition of PDF-containing feldspars is often not reported, but when compositional data have been provided, the feldspars are more often of the low-Ca (An <30) plagioclase or K-feldspar series rather than Ca-rich plagioclase (Trepmann et al. 2003; Gibson and Reimold 2005; Nagy et al. 2008)

Extinction-angle distribution of plagioclase feldspars in

The general Granite and Alkali Feldspar Granite definition can be stated as: Granite is a very hard, granular, crystalline igneous rock which consists mainly of quartz, mica, and feldspar and is often used as building stone. animals and organisms which are now extinct, as rocks are present from millions of years Alkali Feldspar: Monoclinic: Anthophyllite: Colourless: Low to Moderate. 0.013 up to mid 2 nd order: Moderate: Occurs in Mg-rich metamorphic rocks (e.g. low-grade metabasites) / Often with Talc / Like Actinolite but parallel extinction / Length Slow: Good. 2 sets at 124° (Amphibole Cleavage) Straight: Prisms: Large 70-90° Positive.

Augite is a clinopyroxene. Clinopyroxenes and orthopyroxenes are easily distinguished in thin section by their extinction angles: clinopyroxenes have inclined extinction, and orthopyroxenes have parallel extinction. Physical Properties. Chemical formula. (Ca,Mg,Fe,Na) (Mg,Fe,Al) (Si,Al) 2 O 6 Extinction - inclined. Comments - show multiple 'albite' twinning; alters to montmorrillonite or kaolinite. anhedral crystal of plagioclase. XPL. Fish Canyon Tuff. Plagioclase with carlsbad-albite twins. XPL

The general Basalt and Alkali Feldspar Granite definition can be stated as: Basalt is a common extrusive igneous rock formed by the rapid cooling of basaltic lava exposed at or very near the surface of Earth. On the other hand, Alkali feldspar granite, also known as red granite, is a felsic igneous rock and a type of granite rich in the mineral. Plagioclase - (series of minerals in the feldspar group), from Greek for oblique and fracture, in reference to the oblique angle between its best cleavages. Anorthite (Ca %90-100 - Na %10-0) - from Greek for not straight, because of its triclinic symmetry. Bytownite (Ca %70-90 - Na %30-10) - locality at Bytown (now the city of Ottawa), Canada.. 1. Introduction. Quartz is the main mineral responsible for triggering the alkali-silica reaction (ASR) in concrete structures [1,2,3].This mineral has a tetrahedral coordination of silicon (Si) by oxygen (O) stable, but due to tectonic stresses its crystalline structure undergoes displacements and deflections [].The displacement of the crystalline structure of quartz leads to changing the.

The alkali feldspar has first-order grey interference colours. The crystal is a simple twin, its twin plane is defined by the slight difference in interference colours (light and dark grey). Therefore the adjacent twin domains would go into extinction at different times Microcline. Feldspar Group. monoclinic (-) Relief - low. Colour - colourless. RI - 1.518-1.529. Birefringence - 0.006-0.010. Interference colours - low first order

Alkali feldspar granite is pink in fresh exposure and altered patina. The rock is foliated, coarse grained, even grained or K-feldspar porphyritic (phenocrystals 1-3 cm long, locally up to 5 cm), which is generally perthitic. In thin section, granite contains quartz in large polygonal zones and has subgrains Alex Strekeisen - I vetrini della mia fantasia. Biotite - K(Mg,Fe 2+) 3 [AlSi 3 O 10 (OH,F) 2 Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg,Fe) 3 AlSi 3 O 10 (F,OH) 2.Biotite is a solid solution between the end members Phlogopite KMg 3 AlSi 3 O 10 (OH) 2 and Annite KFe 3 AlSi 3 O 10 (OH) 2, although pure Annite does not occur in. 01-jun-2018 - Alkali feldspar (var. microcline) with tartan twinning and perthitic texture (the light-colored fuzzy patches). XPL Oct 2, 2020 - Explore Bryn Mawr College Mineralogy's board Minerals in Thin Section, followed by 147 people on Pinterest. See more ideas about minerals, geology, metamorphic rocks

Feldspar grains initially showing mechanical twinning will develop undulose extinction, subgrains, and progressively new recrystallized grains, which will compound the quartz-feldspathic matrix . At this point, the porphyroclast shape may reflect the deformation pattern and stress field, mainly if they are asymmetrical, as feldspar fish, when. 28-jul-2018 - Biotite (XPL) showing mottled birdseye extinction. Pinterest. Verkennen. Gebruik de pijltjes omhoog en omlaag om door resultaten van automatisch aanvullen te navigeren en druk op Enter om een resultaat te selecteren. Gebruikers van een touchscreenapparaat kunnen verkennen met aanraking of swipe-gebaren. Inloggen crystal zoning A texture developed in solid-solution minerals and characterized optically by changes in the colour or extinction angle of the mineral from the core to the rim. This optical zoning is a reflection of chemical zoning in the mineral. For example, a plagioclase can be zoned from a Ca-rich core to an Na-rich rim. Zoning results from the mineral's inability to maintain chemical. Aug 3, 2021 - Explore Bryn Mawr College Mineralogy's board Optical Microscope Properties and Techniques on Pinterest. See more ideas about optical microscope, microscope, geology Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar. In addition to albite, barium feldspars are also considered both alkali and plagioclase feldspars

Alkali feldspar · 1A Collections

See what Bryn Mawr College Mineralogy (BMCmineralogy) has discovered on Pinterest, the world's biggest collection of ideas Feldspar deformation behavior includes fractures, cataclasite flow, grain-scale faults, patchy undulose extinction, sub-grains with vague boundaries (< 400 °C); internal microfracturing, tapering deformation twins, bent twins, undulose extinction, kink bands (400-500 °C), bulging and subgrain migration, and scarce grain boundary migration. alkali feldspar grow radially from a common center - Branching quartz rods set in a single crystal of feldspar - The quartz rods all go extinct at the same time, indicating that they are all part of the same larger crystal - A coarser variation of granophyric texture is referre Extension of the single diffusion domain/activation energy closure model of Dodson to apply to minerals with a discrete distribution of domain sizes appears to reconcile {sup 40}Ar/{sup 39}Ar age spectra of alkali feldspars with their associated Arrhenius plots. However, small remaining. dence of (AU) on the degree of (Si,Al) disorder in alkali feldspars in general is discussed. In an accompanying pa-per (Armbruster et al., 1990), the effect of experimental 0003404x/90/ I 02-0 I 4 I $02.00 parameters on isotropic displacement parameters (,8 values) has been investigated for low albite. (Si,Al) order-disorder in alkali feldspars

Alkaline rocks associated with all tectonic environment including the Ocean basin. Rocks may be considered alkaline in various ways. In alkali feldspar the molecular ratio of Na 2 O+K 2 O :Al 2 O 3:SiO 2 = 1:1:6 If a rock is called alkaline then it contain more proportion( Na 2 O+K 2 O: Al 2 O 3:SiO 2) of 1:1:6 . Various types of alkaline igneous rocks are * The mildly alkaline series (e.g. Hawaii): Ankaramite (alkali picrite), Alkali Basalt, Hawaiite, Mugearite, Benmoreite, Trachyte is discussed in Section 14.3 (see Fig. 14-2). Chapter 19: Continental Alkaline Magmatism Alkaline rocks generally have more alkalis than can be accommodated by feldspars alone

REE mineral chemistry and the nature of REE mineralization

12. What are the characteristics of Feldspars? 13. What is the overall structure of the family of Feldspar minerals? How do these plot on a tertiary diagram? 14. What are Alkali Feldspars? What are the most common types? What is the general chemical composition? What are the distinguishing characteristics that allow you to identify these? 15 Trachyte is an igneous volcanic rock with aphanitic to porphyritic texture. It is volcanic equivalent of Syenite. Major or essential minerals are alkali feldspar with less amount of plagioclase, quartz or feldspathiod Extinction - inclined. Comments - Often shows simple 'Carlsbad' twinning; alters to the clay minerals illite, kaolinite and montmorrillonite. Carlsbad twinned crystal of orthoclase. XPL. Fish Canyon Tuff . Fragments of orthoclase, showing concentric zoning. XPL. Fish Canyon Tuff . zoned crystal of orthoclase. green-colored olivine (a group of minerals ranging from Fe 2 SiO 4 to Mg 2 SiO 4) and pyroxene (minerals ranging from FeCaSi 2 O 6 to MgCaSi 2 O 6). These ferro-magnesia They generally display strained extinction and are occasionally aggregated together in irregular clusters. Also present are occasional/ subangular feldspar grains, up to 1 m in diameter. The feldspar grains are generally fresh and display twinning which indicates that both plagioclase and alkali feldspar are present (plate 1)

Feldspar - Wikipedi

extinction due to stress. Occasionally, it is inter- grown with K-feldspar, forming a graphic texture. The alkali feldspars are mainly microcline perthite with faint cross-hatched twinning. The plagioclase is oligoclase with An = 16-l 9. The albite twinning shows some bending and gliding due to deformation are dominated by a microcrystalline groundmass consisting of alkali feldspars (Ab9,0r2AnS to Ab140r85hl), plagioclase feldspars (h13Ab,0r3), and augite Large quartz crystals and aggregates of quartz crystals with undulose extinction are found imbedded in the groundmass of these clasts

Sample P13, red circle - growth twinned alkali feldspar with perthitic intergrowth. Make a sketch of perthite texture. Label the diagram. Sample P3, red circle - growth twinned plagioclase grain. Why the change in extinction between twin sides? Why the near-radial distribution of slight changes in extinction? Sample P3, green circle. Alkali-feldspars for the most part are locked within igneous lithics, and range in form from orthoclase +/- minor microperthite stringers, through to microcline intercalated with blocky extinction (strain), although some large quartz domains appear ubgrain to exhibit some (quartz and feldspars), both in hand-sample and thin-section been deformed, and exhibits what is called undulose extinction . That is, the grain does not go extinct all at once, but rather extinction sweeps across the ALKALI FELDSPARS Microcline and orthoclase are polymorphs. That is, they have the sam The alkali release of aggregates can constitute a source of alkalis in concrete exposed to wet environment for long time. Feldspars are one of the minerals that can release alkalis to the concrete with the time. Pint= Internal perimeters with individualised phases of undulose extinction

The lower (oldest) boundary is set at the Permian extinction. The upper (youngest) boundary is set at the Cretaceous extinction. MeV Abbreviation for millions of electron volt. microcline A clear, white to gray, brick-red, or green mineral of the alkali feldspar group: KAlSi 3 O 8. It is the fully ordered, triclinic modification of potassium. Two main varieties of alkali feldspar occur in the Kalgan volcanic rocks. One is high temperature variety-low sanidine (-)2V=26°−40°, distributed mainly in the rhyolite and glassy rocks; another is the intermediate temperature variety-high orthoclase (-)2V=40°-62° , found mostly in the quartz porphyry In intermediate-silicic volcanics, plagioclase is usually the most abundant phenocryst phase and generally displays complex oscillatory zoning. Quartz is the next most common felsic mineral, whereas alkali feldspar is not common in calc-alkaline volcanic rocks and is restricted only to the alkaline series Orthoclase (endmember formula K Al Si 3 O 8) is an important tectosilicate mineral which furms igneous rock.The name is frae the Greek for straight fracture, acause its twa cleavage planes are at richt angles tae ilk ither. Alternate names are alkali feldspar, potassium feldspar an K-feldspar.The gem kent as muinstane is lairgely componed o orthoclase.. 2. Meso- and microscopic textural features of the sub-magmatic deformed peralkaline alkali-feldspar granite of the Papanduva Pluton, Morro Redondo Complex (sample MR-03). (A) Macroscopic 'protomylonitic' aspect defined by elongated and rounded arfvedsonite and alkali feldspar megacrystals in a fine-grained quartzofeldspathic matrix

The most typical Q1, as well as the Q2 facies, display equi to inequigranular hypidiomorphic textures defined by slightly larger tabular alkali feldspar crystals, deformed quartz with undulose extinction and deformation lamellae, plagioclase, and interstitial biotite (Figs. 7a, b). Ca-amphibole is occasional in the grayish variety 1. A rock hand sample is examined in thin section. The microscope has a grid reticle. Under low magnification, the minerals are identified where every horizontal and vertical line cross. The results are Quartz 22, Orthoclase (an Alkali Feldspar) 55, Plagioclase (not Albite) 48 Migmatitic leucosomes composed of alkali feldspar and blue quartz cut segregation layering, and locally define attenuated isoclinal folds. This unit surrounds pods of layered pyroxene granulite (Ypg), and is cut by Grenville-age metaplutonic rocks including porphyroblastic biotite-plagioclase augen gneiss (Ybg) and alkali feldspar granite (Yal)

Thin Section Petrology Databank - Minerals - Perthiteminerals (1) - 1 Actinolite PPL has a crystal habit

Feldspar Distinctions, Characteristics & Identificatio

Evidence for High Temperature Deformation from the Feldspars The principal textural feature of all the GRB rocks is that they are strongly deformed. Typically, large (2 to 7 mm), strained grains of plagioclase and K-feldspar are embedded in a matrix of much smaller (0.1 to 0.2 mm), polygonal, and generally strain-free, quartz, plagioclase an (1985). A model for the irradiative coloration of smoky feldspar and the inhibiting influence of water. (1986). A model of water allocation in alkali feldspar, derived from infrared-spectroscopic investigations. (1993). A new look at stable isotope thermometry. (1986). A spectroscopic study of blue radiation coloring in plagioclase. (1985)

LabFinal_ErinGross - Geology 360 with Brown at UniversityLecture 3 feldspar group and its applicationK-feldsparPlagioclase - WikipediaRock forming minerals - Earth Science 114 with Spera atSerpentine - NOVA Mineralogy

Alkali feldspars tend to display simple Carlsbad twinning, though Carlsbad twinning can be found in all feldspars (Rothwell, 1989, p.74). Grid (cross-hatched polysynthetic) twinning in two directions is a diagnostic characteristic of microcline, and lamellar (multiple) twinning occurs mainly in plagioclase (Rothwell, 1989, p.74) Basal sections will show symmetrical extinction, with elongate sections showing parallel extinction along (100) and inclined extinction (10-21°) along (010) and length slow. Tremolite is distinguished from anthophyllite by the inclined extinction and from hornblende by the greater 2V and larger degree of inclined extinction Times New Roman Monotype Sorts Wingdings Default Design Melt-crystal equilibrium 1 Melt-crystal equilibrium 2 - miscibility Ternary Diagrams Combining phase and composition diagrams for mineral groups Feldspar Group Tectosilicates Feldspar Group - Albite-Anorthite series Feldspar Group - Albite-Anorthite series Slide 9 Staining technique.