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glaucophane interference colors

Talc. IG16-36 Pyroxenes Omphacite in a glaucophane schist.€ Omphacite is an Na-Ca-Mg-Al pyroxene, and is the location of some of the albite component in this feldspar-free rock. Epidote is a common … - Glaucophane Subgroup: Alkali Amphiboles, formed in Na-rich environments, associated with subduction zone chemistry Distinguishing Features: 120° cleavage Moderate to high relief Biaxial Medium interference colors Fibrous habit Photomicrograph of glaucophane in an eclogite under plain polarized light, showing distinct color and 120° cleavage. Brittle. In Greek, glaucophane means "blue appearing". Photomicrograph in plane polarized light with the stage rotated 90 degrees from above picture. Note the anomalous blue-gray interference colors in the glaucophane in this slide. Distinguished from other amphiboles by distinct blue color Chlorite - (Mg,Fe 2+,Fe 3+,Mn,Al) 12 [(Si,Al) 8 O 20](OH) 16 Chlorite is the group name for about 10 related minerals. The blueschist metamorphic facies gets its name from abundant blue minerals glaucophane and lawsonite. Glaucophane [Na 2(Mg,Fe)3Al2Si8O22 (OH)2] is a sodic amphibole that characterizes the subduction-related blue-schist facies. Interference colors are first order gray to white, like quartz and feldspar. Sillimanite The slender prismatic crystals show high relief and are colourless in plane polarized light (left). Characteristics. light. Photomicrograph of glaucophane in plain polarized Associated with lawsonite, pumpellyite, chlorite, albite, quartz, jadeite, and members of epidote group. NOR-281 Glaucophane is the name of a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula ☐Na2(Mg3Al2)Si8O22(OH)2. The blue color is very diagnostic for this species. Uniaxial/Biaxial: Uniaxial (-) Optic axial angle (2V): – Glaucophane is named for its typical blue color. There is also a rare amphibole called holmquistite, chemical formula Li2Mg3Al2Si8O22(OH)2, which occurs only in lithium-rich continental rocks. From RRUFF. Note the anomalous blue-gray interference colors in the glaucophane in this slide. The mica flakes show obvious mottled 2nd order interference colors .The epidote grains are hard to pick out in XP light It appears with brilliant interference colors throughout the thin section. (blue tourmaline is darkest w/ c-axis perpendicular to vibration direction Maximum interference colors are first order red or second order blue, with decreasing order correlating to decreasing Fe content. The interference color chart is the same one as in the third edition 18 years earlier; now, however, it is no longer tipped in, but has been bound in, with the unfortunate consequence of losing the center portion of the chart (lost is the birefringence interval between 0.021 and 0.023) (Figure 18). The blue color is very diagnostic for this species. Specimens Glaucophane is named from its typical blue color (in Greek glaucophane means " blue appearing "). In hand specimen it is dark brown to black in color and shows the characteristic amphibole cleavage. Do the measurements on more than one grain. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.[1]. To the left is a photomicrograph of glaucophane. Anthophyllite is distinguished from … Glaucophane forms a solid solution series with ferroglaucophane (Na2(Fe,Mg)3Al2Si8O22(OH)2). In XP light the chlorite shows anomalous interference colors, the glaucophane shows 2nd order interference colors, in places somewhat masked by the blue color of the mineral. There is no twinning in glaucophane. Crocidolite is called the "Blue Asbestos", because it is strongly pleochroic, ranging from Prussian blue and indigo blue to yellow green. Extinction angle: Parallel / 0° / straight Twins: Apatite twins are rare. Click the thumbnail to see a rollover image of the bird's eye texture when the crystal is close to extinction. The two endmembers are indistinguishable in hand specimens and are strongly pleochroic. from other amphiboles. • Interference colors: Low, from I order to II order. has a parallel extinction when viewed under cross polars. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. Riebeckite is the name used for minerals of the glaucophane-crossite-riebeckite series in which iron is predominant over magnesium and aluminum. chlorite schist pyrite; Chlorite_schist; Chlorite is the organization name for approximately 10 related minerals.However, the time period Chlorite may be used each to explain the organization in fashionable, or as a specific term to explain any inexperienced member of the Chlorite institution whose precise identity isn’t always realistic to be decided. The blue color blueschists is due to the presence of this blue amphibole. Glaucophane is a sodium magnesium iron aluminium silicate hydroxide mineral, found in blueschist facies subduction zones. To the left is a photomicrograph of glaucophane, the lavender colored mineral. Riebeckite ... and show very low order interference colors due to its low birefringence. The Mineral glaucophane Glaucophane is named from a combination of the Greek words Glaukos, meaning "blue", and Phainelein, meaning "appearance", alluding to its bluish color. Note the parallel extinction of one of the crystals and the end on view of Blue pleochroism in thin section/grain mount distinguishes Rio Oremo, Chiavolino, Pollone, Biella Province, Piedmont, Italy Field of View: 8 mm I believe the amphibole has been etched out of calcite. Tends to Ferroglaucophane is similar to glaucophane but is slightly denser and hence increased specific gravity. Blue in color under regular lighting, and often found in differing shades Anomalous interference colors: blue and brown. Click on the image to see a pleochroism rollover. As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. The blue color is very diagnostic for this species. of polarizer). • Relief: Moderate. fast. Inclined extinction. Glaucophane crystallizes in the monoclinic system. Muscovite sample W-12 in cross-polarized light. Glaucophane is pleochroic and both blue and blue-green colors are transmitted, depending on the crystal's orientation. Distinct pleochroism: X= colorless, pale blue, yellow; Y= lavender-blue, bluish green; Z= blue, greenish blue, violet. Glaucophane - Na 2 Mg 3 Al 2 Si 8 O 22 (OH) 2. Glaucophane: Glaucophane . • Color: Blue • Pleochroism: From blue to violet. Darkest when c-axis parallel to vibration direction of lower polarizer The blue color blueschists is due to the presence of this blue amphibole. The interference colors of clinozoisite are anomalous, ranging from anomalous first order Berlin blue and brown for Fe-poor varieties, to anomalous first order lemon yellow for Fe-rich ones. Different minerals display different ranges of interference colors, so color variation is a useful tool for mineral identification. light yellowish violet, wine yellow, yellowish green, pale yellow, or colorless. If the interference colors compound the sample is length slow, if they subtract the sample is length fast. In thin-section, glaucophane is distinct due to its purple-blue-yellow trichroism. Hypersthene : Hypersthene . It is pleochroic in tints of brown. Parting on {100}, conchoidal to uneven fracture. Glaucophane, along with the closely related mineral riebeckite, to which it forms a series with, and their intermediate crossite, are the only well known amphiboles that are commonly blue. Plane/cross-polarized light, field width is 1.2 mm. the thickness of the slide by comparison with the standard interference colors for quartz and plagioclase. To the left is a photomicrograph of glaucophane. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. Glaucophane is named for its typical blue color. Roll over image is the same photomicrograph in cross polarized Glaucophane has length slow, riebeckite length Amanda Nyren (06), Bridget Mahoney (MHC '06), Camille Dywer ('14). Click on the image to see a pleochroism rollover. Glaucophane forms a series with the less-common Ferro-glaucophane, where Glaucophane is the magnesium-rich end member and Ferro-glaucophane is the iron-rich end member. Orthopyroxenes are noted for having low, first-order interference colors. Glaucophane generally forms in blueschist metamorphic rocks of gabbroic or basaltic composition that are rich in sodium and have experienced low temperature-high pressure metamorphism such as would occur along a subduction zone. And interference colors depend on grain orientation, so different grains of the same mineral in one thin section normally display a range of interference colors. It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue. ... anomalous blue interference colors. Cross polarized light, 100x. • Cleavage: Typical amphibole cleavage intersect at about 58° and 122°. In thin section, it shows high relief with a characteristic green - brown - yellow pleochroism. In one of the slides there is an irregular-shaped mineral of a light brown color and cut by intersecting cracks. Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. light. It is probably best know for its low hardness. Interference color: Order II Extinction angle: 36 – 45° Twins: Twins with {100} as twin-plane are known. In Greek, glaucophane means "blue appearing". Note the varying shades of blue that are observed in plain polarized Lavender blue, blue, dark blue, gray or black. Glaucophane also It is more commonly euhedral than quartz in plutonic rocks. Although it has a micaceous structure, it is so easily deformed, that crystals are rarely seen. pleochroism. Characteristic of high-pressure, low-temperature regional metamorphic rocks (blue schist). Glaucophane's hardness is 5–6 and its specific gravity is approximately 3–3.2. Basal sections will show symmetric extinction, with elongate sections displaying parallel extinction and length slow. Cross sections are dark between crossed polars. However, the term chlorite can be used both to describe the group in general, or as a specific term to describe any green member of the Chlorite group whose exact identity is not practical to be determined. Note the anomalous blue-gray interference colors in the glaucophane in this slide. The muscovite alteration products are easily visible here, but the Mg-rich chlorite is not so visible because of its low birefringence. Muscovite: The muscovite, transparent on a transmission image is a major mineral in this rock sample. Glaucophane is the magnesium-rich endmember and ferroglaucophane is the iron-rich endmember. the glaucophane grades over into a green hornblende. Photomicrograph in plane polarized light showing lavender blue pleochroism. For many years, holmquistite was mistaken for glaucophane, as the two look identical in thin section. Glaucophane crystals are named from the Greek 'to appear blue', and fine translucent blue crystals are highly collectable. Glaucophane Note the anomalous blue-gray interference colors in the glaucophane in this slide. Interference color: Order I (black, gray to white). Uniaxial/Biaxial: Biaxial (+) Optic axial angle (2V): 2V measured: 58 – 83°, calculated: 74 – 88° http://rruff.geo.arizona.edu/doclib/hom/glaucophane.pdf, http://webmineral.com/data/Glaucophane.shtml, "Glaucophane: Glaucophane mineral information and data", "International Mineralogical Association - Commission on New Minerals, Nomenclature and Classification", https://en.wikipedia.org/w/index.php?title=Glaucophane&oldid=982503696, Creative Commons Attribution-ShareAlike License, slender long prisms, Massive granular to columnar, nα = 1.606 - 1.637 nβ = 1.615 - 1.650 nγ = 1.627 - 1.655, This page was last edited on 8 October 2020, at 15:22. Hornblende Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. Talc has the chemical formula - Mg 3 Si 4 O 10 (OH) 2. Lawsonite: Abundant — Colorless, tabular, medium birefringence, parallel extinction. Darker with increasing Fe content. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. Hornblend : Hornblende . pleochroism. The relief is high, and the interference colors are of the third or fourth 349 Glaucophane: Rare with characteristic blue color Sphene/leucoxene: Minor Jadeite (CPX): Abundant — forms radiating aggregates with lawsonite. light. On the reflection image (left below), the muscovite appears dark due to the light absorption of the minerals deeper in the section (glaucophane) in hand sample. Glaucophane [Na 2 (Mg,Fe) 3 Al 2 Si 8 O 22 (OH) 2] is a sodic amphibole that characterizes the subduction-related blue-schist facies. Alex Strekeisen - I vetrini della mia fantasia. Color: Blue Gray: Hardness: 6-6.5: Specific gravity: 3.1 to 3.2: Cleavage/fracture: Two perfect prismatic {110}/ uneven: Luster: Vitreous: Transparency: Transparent to translucent: Streak: White to very light blue: δ: 0.01 – 0.02: PPL: Colorless to blue or violet Often strongly pleochroic: XPL: Up to 2 nd order interference colors Interference color may be masked by mineral color of blue. The anomalous interference colors are the result of strong dispersion of the 2V. Glaucophane in a blueschist.€ As with most monoclinic amphiboles, glaucophane has birefringent colors in the lower second order. Blackish-blue fibrous aggregate of glaucophane crystals,Cazadero, Sonoma County, California, USA. Light blue in thin section. Click on the image to see a larger image with a rollover of cross polars.

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