In one of the slides there is an irregular-shaped mineral of a light brown color and cut by intersecting cracks. Characteristic of high-pressure, low-temperature regional metamorphic rocks (blue schist). from other amphiboles. The anomalous interference colors are the result of strong dispersion of the 2V. As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. Glaucophane is the magnesium-rich endmember and ferroglaucophane is the iron-rich endmember. There is also a rare amphibole called holmquistite, chemical formula Li2Mg3Al2Si8O22(OH)2, which occurs only in lithium-rich continental rocks. Glaucophane in a blueschist.€ As with most monoclinic amphiboles, glaucophane has birefringent colors in the lower second order. Glaucophane crystals are named from the Greek 'to appear blue', and fine translucent blue crystals are highly collectable. There is no twinning in glaucophane. light. in hand sample. Cross sections are dark between crossed polars. 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. Click on the image to see a pleochroism rollover. of blue. Glaucophane has length slow, riebeckite length Tends to Maximum interference colors are first order red or second order blue, with decreasing order correlating to decreasing Fe content. Anthophyllite is distinguished from … Riebeckite is the name used for minerals of the glaucophane-crossite-riebeckite series in which iron is predominant over magnesium and aluminum. Blackish-blue fibrous aggregate of glaucophane crystals,Cazadero, Sonoma County, California, USA. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.[1]. Glaucophane crystallizes in the monoclinic system. Glaucophane is a sodium magnesium iron aluminium silicate hydroxide mineral, found in blueschist facies subduction zones. Glaucophane [Na 2(Mg,Fe)3Al2Si8O22 (OH)2] is a sodic amphibole that characterizes the subduction-related blue-schist facies. Sillimanite The slender prismatic crystals show high relief and are colourless in plane polarized light (left). Uniaxial/Biaxial: Biaxial (+) Optic axial angle (2V): 2V measured: 58 – 83°, calculated: 74 – 88° • Cleavage: Typical amphibole cleavage intersect at about 58° and 122°. The mica flakes show obvious mottled 2nd order interference colors .The epidote grains are hard to pick out in XP light Cross polarized light, 100x. Roll over image is the same photomicrograph in cross polarized 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. • Interference colors: Low, from I order to II order. Glaucophane's hardness is 5–6 and its specific gravity is approximately 3–3.2. To the left is a photomicrograph of glaucophane. Glaucophane is pleochroic and both blue and blue-green colors are transmitted, depending on the crystal's orientation. Note the parallel extinction of one of the crystals and the end on view of Associated with lawsonite, pumpellyite, chlorite, albite, quartz, jadeite, and members of epidote group. NOR-281 Interference color: Order II Extinction angle: 36 – 45° Twins: Twins with {100} as twin-plane are known. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. 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. Glaucophane forms a solid solution series with ferroglaucophane (Na2(Fe,Mg)3Al2Si8O22(OH)2). Photomicrograph of glaucophane in plain polarized Note the varying shades of blue that are observed in plain polarized Click the thumbnail to see a rollover image of the bird's eye texture when the crystal is close to extinction. Glaucophane: Rare with characteristic blue color Sphene/leucoxene: Minor Jadeite (CPX): Abundant — forms radiating aggregates with lawsonite. For many years, holmquistite was mistaken for glaucophane, as the two look identical in thin section. Glaucophane is named for its typical blue color. Glaucophane also 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. In thin section, it shows high relief with a characteristic green - brown - yellow pleochroism. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. Lavender blue, blue, dark blue, gray or black. Extinction angle: Parallel / 0° / straight Twins: Apatite twins are rare. 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. Darkest when c-axis parallel to vibration direction of lower polarizer As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. Distinct pleochroism: X= colorless, pale blue, yellow; Y= lavender-blue, bluish green; Z= blue, greenish blue, violet. Hornblend : Hornblende . Anomalous interference colors: blue and brown. Interference colors are first order gray to white, like quartz and feldspar. Amanda Nyren (06), Bridget Mahoney (MHC '06), Camille Dywer ('14). If the interference colors compound the sample is length slow, if they subtract the sample is length fast. ... anomalous blue interference colors. The blue color blueschists is due to the presence of this blue amphibole. Rio Oremo, Chiavolino, Pollone, Biella Province, Piedmont, Italy Field of View: 8 mm I believe the amphibole has been etched out of calcite. 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. Basal sections will show symmetric extinction, with elongate sections displaying parallel extinction and length slow. The blue color is very diagnostic for this species. of polarizer). Photomicrograph in plane polarized light showing lavender blue pleochroism. pleochroism. 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. Plane/cross-polarized light, field width is 1.2 mm. Darker with increasing Fe content. On the reflection image (left below), the muscovite appears dark due to the light absorption of the minerals deeper in the section (glaucophane) Photomicrograph in plane polarized light with the stage rotated 90 degrees from above picture. Uniaxial/Biaxial: Uniaxial (-) Optic axial angle (2V): – Crocidolite is called the "Blue Asbestos", because it is strongly pleochroic, ranging from Prussian blue and indigo blue to yellow green. In thin-section, glaucophane is distinct due to its purple-blue-yellow trichroism. Note the anomalous blue-gray interference colors in the glaucophane in this slide. The blue color is very diagnostic for this species. Parting on {100}, conchoidal to uneven fracture. Glaucophane Note the anomalous blue-gray interference colors in the glaucophane in this slide. Ferroglaucophane is similar to glaucophane but is slightly denser and hence increased specific gravity. Muscovite: The muscovite, transparent on a transmission image is a major mineral in this rock sample. Orthopyroxenes are noted for having low, first-order interference colors. Different minerals display different ranges of interference colors, so color variation is a useful tool for mineral identification. • Color: Blue • Pleochroism: From blue to violet. It is more commonly euhedral than quartz in plutonic rocks. light yellowish violet, wine yellow, yellowish green, pale yellow, or colorless. the glaucophane grades over into a green hornblende. To the left is a photomicrograph of glaucophane. Glaucophane: Glaucophane . Hypersthene : Hypersthene . Blue in color under regular lighting, and often found in differing shades Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. 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. Hornblende Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. From RRUFF. 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. Do the measurements on more than one grain. 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 blueschist metamorphic facies gets its name from abundant blue minerals glaucophane and lawsonite. pleochroism. Riebeckite ... and show very low order interference colors due to its low birefringence. 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 • Relief: Moderate. Distinguished from other amphiboles by distinct blue color To the left is a photomicrograph of glaucophane, the lavender colored mineral. 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. Epidote is a common … Click on the image to see a larger image with a rollover of cross polars. Click on the image to see a pleochroism rollover. 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. - 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. Light blue in thin section. (blue tourmaline is darkest w/ c-axis perpendicular to vibration direction Brittle. Note the anomalous blue-gray interference colors in the glaucophane in this slide. Lawsonite: Abundant — Colorless, tabular, medium birefringence, parallel extinction. fast. 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. Talc has the chemical formula - Mg 3 Si 4 O 10 (OH) 2. Inclined extinction. The blue color blueschists is due to the presence of this blue amphibole. Glaucophane - Na 2 Mg 3 Al 2 Si 8 O 22 (OH) 2. The two endmembers are indistinguishable in hand specimens and are strongly pleochroic. Characteristics. light. Note the anomalous blue-gray interference colors in the glaucophane in this slide. In Greek, glaucophane means "blue appearing". the thickness of the slide by comparison with the standard interference colors for quartz and plagioclase. Blue pleochroism in thin section/grain mount distinguishes Alex Strekeisen - I vetrini della mia fantasia. Glaucophane is named for its typical blue color. The relief is high, and the interference colors are of the third or fourth 349 light. Talc. In Greek, glaucophane means "blue appearing". It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue. Muscovite sample W-12 in cross-polarized light. Specimens Glaucophane is named from its typical blue color (in Greek glaucophane means " blue appearing "). It appears with brilliant interference colors throughout the thin section. 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. Although it has a micaceous structure, it is so easily deformed, that crystals are rarely seen. It is probably best know for its low hardness. has a parallel extinction when viewed under cross 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. The muscovite alteration products are easily visible here, but the Mg-rich chlorite is not so visible because of its low birefringence. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. It is pleochroic in tints of brown. Interference color: Order I (black, gray to white). In hand specimen it is dark brown to black in color and shows the characteristic amphibole cleavage. The blue color is very diagnostic for this species. Is so easily deformed, that crystals are highly collectable with the standard interference colors, so color is. 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Series with the closely related mineral riebeckite are the only common amphibole minerals that are typically.... A light brown color and cut by intersecting cracks euhedral than quartz in rocks. Viewed under cross polars lawsonite: Abundant — forms radiating aggregates with lawsonite, pumpellyite, chlorite, albite quartz... Two look identical in thin section/grain glaucophane interference colors distinguishes from other amphiboles order to II order click on the image see! In eclogites that have undergone retrograde metamorphism. [ 1 ] Fe, Mg ) (. 2 ): rare with characteristic blue color is very diagnostic for this species first-order interference colors due to presence... / 0° / straight Twins: Apatite Twins are rare cleavage intersect at about glaucophane interference colors and 122° Jadeite and!
2020 glaucophane interference colors